I'm a guy who needs help.

I need advice and heard this was a great place.... I have sex with a condom and pullout and am still stressed that I get a girl/gf pregnant. I'm 18 and I feel like less of a man that I get so scared, so freaked out... I feel bad.  Idk why I get so scared.  I never had a break, or slip off, I used the condom the whole time.  And check for leaks after.  Yet I'm so stressed I break out and feel horrible for weeks.... Am I less of a man?  My gf doesn't really get nervous ever, but me, I am so tense after sex.... 
Sometimes I feel so sad and I feel like I'm the boy, so I'm supposed to be all horny, but I get so scared and paranoid, and if I have sex on day 1 of her cycle I will be paranoid till the day she gets her period.