pregnant or stress?

i had sex for the first time on april 1. my boyfriend wore a condom, and said it didnt have any tears. my period has been irregular since january. in jan i started the 3rd, in feb i started the 4th, and in march i started the 9th.i havent started yet this month. i got to thinkin about it and read the early pregnancy symptoms, and thats when i started feeling this way. my stomach is tensed up, my upper back kind of hurts(maybe from all the shaking ive been doing) and when i eat i feel like im gonna throw it up.but thats all the symptoms i have of pregnancy. is this stress? or could i possibly be pregnant?