paraguard help

So I have the paraguard iud in for about 3 years now and I haven't had my period since April 20th and ended April 28th I took a tests and came back negative but I've never went without my period and I did spot once and thought I was getting my period so I'm a bit concerned because I'm 15 days late or more because usually if I start my period at the first of the month I'll have in near the middle of the next month and at the end of another month so it's pretty consistent but anyone have any suggestions or if you have experienced the same thing please let me know in the comments but I plan on going to the doctors Wednesday