2 Miscarriages

Haritha
Guys, I had a miscarriage in Jan for the 1st time and I was 4-5 weeks then. Again in May I started ttc and I got pregnant this month and I was 5 weeks yesterday and got miscarried. I had sudden shooting pain in my stomach and I went to washroom where I passed a huge clot. 😭 
When I tested positive (before miscarriage) I got to know that I'm not immune to Rubella. I just want to know what could be the reason for my 2 miscarriages? Is not being immune to Rubella a cause for miscarriages?? 
I'm yet to see my doctor soon. Before I see her, can anyone please put your opinions?