He...wants to marry me!!!

So, my S.O. told me yesterday that he wants to marry me...and well, I just kinda walked away in shock... so I went home and laid in bed for about 3 hours, confused, and I can't debate the pros and cons of being married. I'm only 18, and he's 26. I don't wanna get married yet because I'm soooo young and need to mature a lot more before then, but I've always wanted a family. He needs to take care of his son and ex girlfriend because they live with him, but yet he also wants to marry me while he's really tight on money... what are the pros and cons? Should I do it?...