Hey so this post might get a little long..sorry if it does! I appreciate anyone who replies

So I am 21 and my bf will be 21 next month.. we have been together for 3 years and i love him so much. I've had family members and friends being like oh you still hanging onto that guy? you going to get married? blah blahh. and my mom and grandma have always told me, fairly often actually, the past 3 years that i need to explore, date, meet other guys, have fun ect. cause he was my first real long term relationship(my ex was a short, high school fling that turned out him cheating, but anyways) so my response to them has always been im going to live in the moment and i dont want a break, im happy with him now, there are a lot of assholes in the world, it would break his heart and who stops seeing their best friend anyways!? so I've always just put it in the back of my head because i love him and we both are on the same page..we want to get married around 26/27 and have kids after, be financially able and done school before we move in and not anytime very soon.
I went on a beach holiday with my best friend, sara (lets call her) and a bunch of her guy friends. Long story short, she likes one of them, he always rejects her, they both start hooking up with others on the trip.. she was a mess all week and being nasty to me saying shes jealous, wants the relationship i have, .. that I am flirting with the guy she likes (when he was just being nice since i didnt know the group well) anyways then i was getting depressed cause everyone i went w/ was hooking up and I'd go back to the room from the club missing my bf..she didnt care about my feelings. then the guys knew she was driving me crazy all week and jealous of me and obsessing over a guy who keeps saying it wont work to her.. so they knew i wasnt having a great time and they are nice guys and would hang out, talk, make jokes, ask about my bf, ex's and all that. they would also rate girls and guys on the beach and make noises when they saw a hot girl lol..it was all jokes and my friend found it offensive :/ then one of them i found myself liking (not the one my friend likes!) Well more they all were flattering to make me feel good, not in like a perverted way. But this one guy i liked especially. i got the feeling from him that if i didnt have a bf he would have tried something on me or wanted to go out or dance there or whatever. this guy would compliment my heels, belt, skirt stuff like that and apparently everyone was in the ocean and he made that noise the guys made when they see a hot girl, to me when i was in my bikini! But long story short he didn’t make any moves cause he knew i had a bf and they were just nice guys and there for me during the week.
When i got back i started wondering how many guys i have rejected or could have given a chance that were nice, but i never did cause I am very faithful to my bf. And i was having some thought that i liked this guy and was attracted to him (similar features as my bf) from the group and questioning if i want a break from my bf. But then i decided that I was just a little flattered there and they were just being friendly which is nice but thats it, it was a little flattering and such but no need to give up what my bf and i have cause of these thoughts of “exploring” like my mom and grandma have been telling me.
Now my bf wants to go away a weekend up north to spend together and have sex. He has been extremely patient with it and never has pushed me, but well i know he wants it. (done pretty much everything but actual intercourse) and said if we get there and i dont want to we wont and will just cuddle. hes very respectful and will always stop when i ask.. i dont think guys like that are easy to find. but then i have these feelings from the trip i didn’t like and i don’t know if i should be meeting other people before we do actually get married, if we do.(which i have thought about before that maybe my mom and grandma are right:S ) but its just a look, i dont act on it ever if i think someones hot or something lol Over a year ago I talked to him about it the whole do you think people can just marry there first love without ever meeting anyone else, well he thought i was breaking up, which i wasn’t. He basically said you never know if you’ll get back together and either person could find someone they end up marrying while the other is “exploring” which i agree.
Today when he was saying to go overnight I asked him if he thinks it ok if people have sex before marriage and don’t end up actually marrying that person, cause you just never know the future right. And he said that its ok and he said basically: i love you and care about you baby,i want to lose it to you cause i could see myself marrying you. I can see myself marrying him too and I’ve thought about living with him, what our children would look like, our wedding ect but the future does scare me and if what my mom and grandma are saying about exploring and other options is true.
So to sum up, i do love him, i do see myself having a future with him and i don’t believe i need to wait until I am married for sex..but im scared that if we have sex i’ll be wondering what if i don’t marry him, i don’t want to have sex and then feel like i need to break up before we actually would settle down. Or do you think its just been too much pressure from my mom and grandma? Anyone else ever have this happen? how do you deal with it? And do you think what i was thinking over the trip was just me being flattered and nothing to break up over? we both of course dont know the future so if i feel ready should i go ahead.. i dont feel like i have a lot to lose being with someone 3 years, hes no stranger. even if we didnt get married, its not like i lost it to someone i hardly knew. but i dont want to do it then feel i need a break soon down the road, and break his heart.. but ahh all these break feelings isnt coming from meee..i think I've just had to much pressure and talk of "exploring other options" from my mother and grandma has really affected me over the years