Help! I don't think I'm ovulating

I kind of starting to freak out here. I was on the Mirena for almost 5 years and had it taken out in August. I've had two normal periods since then but have not had a period since early November and all my ovulation tests have been negative since then. pregnancy tests are negative too. I don't think I'm ovulating! Any tips on making your body ovulate? I'm over weight and I am trying to loose weight.  Any other tips? How soon should I see a doctor? When is the best time to test? What brand should I use? I'm using the Amazon clinical guard because they are super cheap. Should I switch brands? Any help is appreciated! Baby dust to all! 😘

Sarah