Honestly at a complete loss.

I skipped my period in March and made a doctor's appointment for April 3rd and started my period the day I went in and I bled till the 8th. I didn't have a period in May or June. I also still have not started. I haven't had a positive at home tests, I got blood work last Wednesday and they said it was negative. I'm at a complete loss. I know I should probably see a doctor, but my old dog really needs to go to the vet because he is sick and its gonna be pricey so I need to put him first. I really wish I knew what was causing this. I think I was usually pretty regular before this, I had never skipped before, but I had been a week or so late. I have no idea what it could be, but I'm worried.