So frustrated right now

Ugh, what the heck is wrong with me? I'm 23 and my husband is 22, so we still have a long time before we should really start worrying, but this month will be the last month of ttc before it'll be a year. I went to the doctor about 4 or 3 months ago, and she said everything is fine and not to be worried. Its soo frustrating. My period is perfectly normal, it comes exactly when its supposed to (31 days) with the variation of 2 or 3 days early or late, So I don't get what the heck is wrong. All my friends that have had babies or are pregnant, I don't really know how long they were trying or whatever but they got pregnant before they'd even been together for a year. And then I have another friend who is younger than me and she had problems with her period where she would skip one or two periods at a time, and she's 7 months pregnant now. So its just like if someone who didn't even regularly get a period can get pregnant why the heck can't I? My husband's cousin even got pregnant, had a miscarriage and got pregnant again within the time that we've been trying. Its just so frustrated watching all these people who you would think would be having problems getting pregnant, and they're getting pregnant way easier and sooner than I am, when I "supposedly" have nothing wrong. Just totally needed to vent all that I just got AF last night after being about 3 days late and getting my hopes up waaay too high, so thanks for listening.