Should I just forget about it or is there anything I could do to convince him?

Convincing people is never a good idea. You can have an honest discussion with your SO and tell him how you feel about something but that's it. You don't want him to feel obliged to do it to keep you happy. Doing anal is a boundary for your SO. Thus be respectful to him and don't talk about "convincing" (or manipulating) him.

Any other guys out there who feel the same way as him and if yes, could you please explain it to me why exactly you hate the though of anal so much?

For everyone it's different. Some people don't want to do anal, others don't like giving or receiving oral. The reasons you will hear from other people might not necessarily be the same for your SO. Why haven't you asked your SO why he doesn't want to try to do anal?

He didn't have much previous experience in sex, if any at all. We started with PIV and a few months into our relationship I asked if he would be up to try something different.

Reading this, it seems that you're really really pushy. In many cases, asking someone over and over without "discussing" the issue thouroughly is counterproductive. You only talk about yourself but not his desires, worries etc. Think about it.

Tbh, I really don't want to do it if he's repulsed by it. But, I miss it. I keep hoping that maybe in a few years he's gonna give it a go... but honestly I don't think that's gonna happen.

So you've never really discussed the reason why he doesn't want to try it. Maybe he just needs time to feel comfortable with his body, maybe it's just something he finds disgusting.... Who knows. You've been together for 2 years and you can't talk about that. Don't hope that something is going to happen. If anal is a must for you, you have to start thinking if you want to stay in this relationship or not.