Hiya
From what you've mentioned, it does sound like OCD. Do you experience anxiety if you don't do all those things? Do you know they are slightly irrational but feel like you have to do them? Are they time consuming?
You should contact your Doctor and describe some of the 'symptoms' and they will probably refer you to a therapist. It all sounds so dramatic but they'll probably give you what I think is called exposure therapy..don't quote me on that though. It's basically a type of therapy where they try and stop you from performing the obsessive and compulsive actions by saying 'just don't do it and see what happens' which can be very (understandbly) distressing at first. It's a little more complicated than that..but that's the basic explanation! Most people with OCD think if they do not perform the action then something bad will happen and/or experience a great deal of anciety if they cannot do the action. The therapy basically teaches you that this isn't the case.
You probably don't want to admit that you do have OCD so you could be in denial. You're right that for some people it's very serious and debilitating but then it can go the other way, in others it's a lot milder. Some of the things you said can be typical fears or bugs, such as the door being cracked open (I happen to hate that too!). But other ones, such as the obsessive cleaning, touching your fingers to letters and counting the clocks is slightly more typical of OCD. There's nothing wrong with admitting you have OCD, it gives you a reason behind your behaviour and means it can lead to treatment.
Saying that, I'm not a professional and that was just opinion, so contact someone who is trained and ask what they think. You could also google OCD and see what websites say but I'm sure you've already done that!