What in the heck did I do wrong?

So to start I've been with my hubby for 3 years pretty much tring to conceive all 3. 2 years ago we conceived but lost our first baby at 5 weeks. I'm a full time step mom to 2 great kids but none of my own. April came round found out the same day as my best friend I was pregnant. I couldn't be more thrilled... thought finally a break for me.... nope 9 weeks in I start the bleed. No baby on ultrasound after. The same day mine was empty she found out she was having twins ... on Christmas...for real it was like God or the universe slapped me dead in the face. Now every time I turn around ppl are getting pregnant.. my 17 year old adopted sister.... all my high school friends. .... every person I know either has babies or is about to. I feel so cold and bitter any more and that's not me. Every one tells me oh well you have step kids ... yes they are my world but I want an ours baby.. i want that bond that they have with their actual mother ... I want to watch my kid grow and walk and talk. I came into my step kids lives when the youngest was 6. I'm going to be 33 soon and I feel like I'll never get to be a mother I'll never get to feel the good and the bad of pregnancy and feel the baby grow inside me...every month I get my period is so devastating... now I get to watch my best friend grow with her babies and it's not her fault but it kills me every time because my brain won't stop thinking "this is where I'd be in my pregnancy if my baby survived" .... sorry I just needed to get that out some place. ... my one person I used to talk to ... I dont feel right now in telling her my feelings I don't want to burden her now with my failings. I just feel so tired....