You know, a two year relationship at your ages (both 18), is a long relationship! And in most long-term relationships, there are ebbs and flows and ups and downs. So it’s normal to feel happy to be together, annoyed at each other, anticipating meeting up, bored — and all sorts of other emotions. I don’t think that ups and downs mean anything bad is happening. However…. trust your instincts. If you feel that he’s losing interest, then try and heat up the spark. Go have an adventure. Take a road trip. See something new, or do something different. Long-term relationships take work, and you have to put some planning and some energy into keeping things fresh.
I hope that helps!