Late period need advice!

Susan

As of today I am 16 days late for my period. I do have a iud so I feel like that's probably why I'm late because it say you can have mild or no period with it sometimes, but I've always had a regular period till now. It's been about a yr since I had a new one put it. My boyfriend claims that 2 out 3 of his kids were conceived while his ex had the iud. Personally I was like no way that's not possible. But he still has me stressing. I've taken 2 test which both have been negative. With my son I knew 1 week after my missed period but I wasnt on borth control with my son. But I never had any pregnancy signs either.... anyways I feel like it would be a waste to go to the dr but my boyfriend thinks I need to go in.... thought??