Love Anxiety! Need support

Lately I have been haunted by some bad thoughts: I can't stop thinking about the moment when my boyfriend and I will break up. I know it's normal to be a bit worried about losing someone you love, but I can't study, I can't breath, my heart beats really too fast, I feel dizzy and nauseous...until I cry, about 3/4 times everyday.

I don't enjoy spending time with him anymore and also texting him scares me. I'm really thinking about breaking up, even if I somehow know it doesn't make sense. But I can't see the point of being with someone I will have to leave.

I'm 17, he's 19 and I've been with my boyfriend for three months. He respects me, loves me, takes care of me. He often talks about our plans for the future.

But I keep thinking about how much I suffered when my big first love left me alone.

I have had to struggle with anxiety many other times, but this time it's destroying my life.

I'm confused. I feel like I want to stay with him forever and I also want to be free because I'm only 17.

Please help me, I'd be so happy if you shared your experience :)

(Sorry for the English, I'm italian🇮🇹 - and this is also my first post!)