TMI mocus plug

When I went to wipe I found this. I was told I have a Bicornuate Uterus. And have to see a fertility specialist. but I am not sure what this is?? my period is 5 days late. I have iud in the right part of my uterus (right horn) it’s not doing anything for my left side. I have not had sex in a little over a month. gained 6 pounds in the past 4 weeks , super moody, boobs are a little sore but not a lot, been sore for last 3 weeks and off and on with being hungry or nauseous. What do you all think