Should I be period in 2 1/2 months

Ok I'm new to this community. So I have two beautiful daughters and in the future we want to try for a son but I wasn't ready so I've had the IUD inserted and it's been 5 years. These past 6-7 months I've been getting my period every two months and it's only for like a day, or I'll just be spotting and that's it. I took a few pregnancy tests and they come out negative but I feel fluttering at times in my stomach. (What is that?) It's hard because I work nights and 40+ hours and I'm always tired. Has this happened to anyone else using the IUD?