TTC for almost 2 years any advice ?

In January it will be two years of ttc #1 
I'm 18. 5'5 & weigh 250 ( when in person I don't look it ) fortunately 👌🏽
I never knew getting pregnant would be so hard. I have a 31 day cycle and my periods last 10 days. 
I just get so depressed every month I honestly think there's something wrong with me 😔