PLEASE RESPOND

My boyfriend and I are sexually active and moments I get scared he came in me but he knows he doesn't. But we typically use condoms. But recently we done it and then couple days later I think I got a UTI and started to freak out. I was suppose to get my period Saturday but it didn't come, today the 6 day without it. And Today is my last day for medicine. Also I have worked out past couple days one days I worked out more then others and past two days I have been in lot pain my whole back hurted, massive headache, super hot and felt cold. Could all of this be due to stress and UTI? Or something different