I'm late, what should i do?

I'm 18 and engaged, i live with my fiance and his mother. I noticed that i am late on my monthly. Yes i did have unprotected with my fiance within the last 2 or 3 weeks. My last period was Feb 23. and there usually normal. I have been getting this cramps but their starting to go away. i wont have any money till my new job (lowe's) deposit's my paycheck in my checking account, and that wont be 'till april 11. by my faince just a job at ollies and he gets paid april 4. i'm actually scared about this, i mean i wouldnt mind having a kid now but i dont know if i'm ready to be a mother. What should i do? please give us some advice.