can I have a baby?????

So I've had a couple pregnancy scares. (I'm 18) and a couple times my man swore he may have came in me ... Well we waited it out and I've never gotten pregnant. (We've been dating for a year and a half.) 
Anyway, I'm scared to death of not being able to have kids. It's one of my biggest fears. Of course I don't want any rn.. But I'm thinking about going to get tested to see if I'm able, just to ease my mind. 
But what are the tests like? What do they do to test you I mean?