Hi Lucy!
Panic attacks are a really horrible experience and can be absolutely terrifying, so I'm very sorry that you're going through that. I have a few ideas that you may or may not have already tried:
1) When you feel like you're about to have a panic attack, or when you're in the midst of one and trying to calm yourself down, it can help to give your mind something else to do that is both soothing and repetitive, and requires some thinking. The 54321 technique is great - you look around at your surroundings and name 5 things you can see, 4 you can touch, 3 you can hear, 2 you can smell, and 1 you can taste. The more detailed and specific you are, the better. Counting up or down by strange numbers (so you really have to think about it) - e.g., 9's, 13's, 17's - might also help. And if you're with another person at the time, and you trust them, it might be helpful to have them walk you through whatever grounding techniques work well for you, since thinking clearly is usually difficult when you're panicking.
2) Some kind of major distraction can be really helpful in sort of re-setting your brain when you feel like you're about to have a panic attack. I suggest something that requires all of your attention and ideally some level of external composure - e.g., if you're at work and can feel yourself beginning to panic, go talk to a customer or your boss. Your goal is basically to interrupt the spiraling thought process that leads to a panic attack, and sometimes having interactions like that can be the "jolt" to your system that you need to kind of reset the situation! Things like engaging podcasts, songs, etc. might also work.
3) I totally agree with the previous user's recommendation to see a therapist! Therapists are awesome people and can make a huge difference. I think one of the most important things they can help you do is become less afraid of your panic attacks - I've found that once they become less scary, they don't happen as often, because fear of having a panic attack can sometimes actually lead to a panic attack. (Super ironic and horrible.) A therapist can help with that!
Hopefully something here helps! I'm sure that dealing with panic attacks for as long as you have been has been really, really rough, but you're awesome for continuing to stick with it and look for ways to get better. I hope things start looking up soon.