Well....IMO, you're NEVER too young to feel what you feel!!!! But, if you're 15 yrs. old, you have A LOT of time to take things s-l-o-w-l-y
You have your whole life ahead of you, and it's fun to date, and have someone with whom you 'connect'....but I would say not to pin your choices down to one strict person! I was there...when I was 16 I hooked up w/ someone (an 'older' guy)...and I was with him for six years...oh how I wish I'd done things differently. I missed out on many of the things that I should've done. Things may be different with you...I don't know if this guy is your age; but if he is, then it's a diff. situation; you're both in the "school and friends" mode now. If he IS older...you should consider thinking about taking a lil' break from the situation...just to assess your feelings. I know it feels like the end of the world, and it hurts SO badly. It won't be like that forever. The pain dulls....fast.
I just think that 15 is too young to limit yourself. And, this is my opinion, and my opinion only (and many may disagree), but USUALLY an intense relationship involves sex (I say usually..not always...some people decide to wait...'specially when they're young)...and *I* think 15yrs. is TOO YOUNG to be sexually active...
If you are writing for advice, that means you're most likely having doubts. Usually when a friend expresses an opinion of this nature, they're right. So listen to your HEAD. NOT your HEART!!! If you two love each other, that's great! No one can tell you otherwise. Is 15 too young for love? No. Just be careful of your choices....and don't think with your hormones! And try to experience everything a young girl SHOULD experience...don't let a relationship take ANY of that away from you!