Is it possible to be allergic to my boyfriends semen? it always burns right after for awhile. we use a condom now but im just curious why?

Not necessarily: You may be reacting to the condoms- either the latex, the lubricant on them, or the spermicide. It's possible you need more lubricant if you are not getting enough vaginal secretions before intercourse. Try a different condom (read the labels to look for a latex free one). Use a good lubricant (non-scented, water based is probably best with condoms). If not better, see your doctor.