Heartbroken

So after af is 3 weeks and still not showing all hpt are negatives and blood tests are apparently negative they can't figure out what's wrong and why there is mucus plug like discharge if not pregnant so tests are going on and all this stuff...we just want our daughter to have a sibling that's all she ever wishes for when she makes wishes it's just all too sad to keep dealing with..its been over 2 years of trying and just getting ready to give up😥