20 & 6 months TTC

Brittany • 20....married since 7.16.14. TTC #1.
Hello everyone, 
​I just turned 20 on August 14. I have been actively TTC for 6 months. (This month, September, is month 6) My dh is 25. We got married on 7.16.14. I am getting so discouraged. I am a bit overweight.... Maybe that's why? But I'm wondering if I'm even able to have children. I do not have any known fertility obstacles. I am not on Bcp or any medications. I haven't charted my intercourse days at the beginning but have been trying! I don't temp because my schedule doesn't allow it. I'm at the point of giving up. My sister is 21 and on baby #3!! It's sooooooo stressful! Please someone give me hope because I'm too exhausts with the TTC train! ? I have my charts posted