I’ll come in here with a different perspective.
Focus on your GCSE’s and still make time for him as it sets you up for the rest of your life. If you don’t get good GCSE’s, you can’t do A Levels, then you can’t go to as good universities etc as they look back as far as gcse grades when making offers.
I was with (who I thought was) the love of my life when i was 16 years old and just started college. I would go to visit him rather than do college work, I would even skip college to see him sometimes. Long term this messed up everything for my future, I had to stay back in first year, behind all of my peer group as I was failing, for him to leave me regardless when we were 17 leaning towards 18. He got bored of me and went off with other people after he grew a big ego. This destroyed me and lead to me doing really poorly, so staying back in college allowed me to do better in my A Levels, although as mentioned, this costed me a lot socially and mentally.
If you both keep making effort there’s nothing to worry about, but first loves aren’t always bound to last, it’s very rare for them to do so. Live in the present, love him and enjoy him while you have him, but if it doesn’t work out, it doesn’t work out. Focus on exams and take life with a pinch of salt. If you’re meant to last, you’ll last. You shouldn’t stress about things like this when there are bigger things to stress about coming up.
I’m sorry your mums not being good with you over you having a boyfriend. It’s wrong of her to be like this. I can relate as my mum was gobsmacked and snooped round my room to look for signs for what I was upto with my first, and she was horrified by it. I think it’s because they don’t like the idea of their children growing into young adults, even though it’s life. And the way it’s being done is NOT the correct way to go about this.
If you want to talk about anything feel free to throw a message as I feel I can relate to you somewhat on this, as i’ve been through similar myself, I’m now coming up for 19 and have come out the other side of things with new perspectives, realising how much I idolised a relationship which was never bound to last, which I didn’t see until after it all ended and I found confidence to move on.
You’re young, naive, and it’s your first time learning to love, so please try not to stress. Just focus on the happy things in your relationship, not the worries!
Hope this helps a little bit.