Can a 16 year old boy really feel deep in love for his girl?

Certainly he can. Back in the 1800's young people were married and raising families at the age you are (I'm not suggesting you do that!) Every so often there are young couples that fall in love deeply and the relationship lasts until the day they die of old age. It's rare, but it happens. One movie I recomment for both men/women of all ages is "Notebook" and it's about a young man from the wrong side of the tracks falling in love with a high society girl. It's an excellent movie and one you should see. Great love story without being too mushy for guys.