Why is getting pregnant so hard?

Why is getting pregnant so hard? My husband and I have wanted children for a really long time but wanted to do it "properly" - not that there's anything wrong with doing it another way but you know - finish school (we've been together since we were 16), go to uni, get jobs, buy a car, buy a house, have a few holidays, get married etc. So now we feel like it's the right time and it's just not happening!

We haven't been trying for that long, only a few months, so I can only imagine how people who have been trying for years without any luck feel but it's so emotionally exhausting! Every month I think, "this could be it", I start getting what I think to be pregnancy "symptoms" and then BFN! It's so stressful and upsetting! And babies are like every where in my life right now - a couple of my friends have just had babies and my sister in law is due any day now - she's on her 4th now in as many years!

Before we started TTC, AF was pretty regular but since we started ttc it is all over the place, starting a week earlier, or being really light (like only when I wipe). I am clearly stressing myself out causing my body to be all weird which clearly isn't helping make said baby but how do I stop putting so much pressure on myself? Does anyone else feel like this? :(