OP, I am biologically infertile, but very fortunate to have adopted (informally - birth mum refused) my late husband's son.
He came into my life when he was 5, after I met his dad, who was the RP.
He's now in his early 20s, still lives at home with me, and brings me happiness every day. We make a great team. TBH it's rare that we "remember" we're not related by blood.
There have been a lot of challenges along the way, mainly due to abuse from his maternal family which has caused him PTSD, social anxiety and depression.
If you feel you are up to the challenge of taking on a child with MH issues/learning difficulties/physical disabilties etc then please consider adoption. But don't feel like you "should" be doing it.
You need to take some time to grieve now for the future you thought was going to happen. It may take you 2-3 years to come to terms with. It may take you 10.
For me, I'd say it was about 5 years from finding out I was infertile. Bearing in mind I'd been TTC for the previous 10 years, endured countless tests, been on Clomid which made me suicidal (and was completely pointless since all tests showed I was ovulating normally, the consultant just threw it at me as a sop to "oh yeah we're trying to help".)
I'm sorry, I didn't want to go on about my own situation.
Please take care OP and definitely get this thread moved.