Hi Snowie - I firstly want to say I am so sorry that you have had to endure the loss of 4 precious babies. I hope you find support here amongst the women, I know it they have all helped me through some very dark days. Please feel free to join us.
I also felt like the world around me was pregnant and it hurt so much to see bellies growing, knowing that mine was now empty. Pregnancy loss is a very lonely place and few people really understand the heartbreak. I can only say that you should ignore people that say you should have had a baby earlier - hindsight is always a great thing - but not exactly helpful. It would have been great to have had babies early, but like you I was single and also I was too busy having a party of a time. We all have our own timelines for these things, and people saying that too you are not helpful nor understand how difficult your losses have been! So big hug
Whereabouts are you located? I know you have had a lot of tests done, but there may be a supportive ob near you that can help. My ob Mark Umstad in Melb specialises in high risk pregs and those that have had previous losses. He is not only thorough but also very compassionate and lovely.