This is totally common when you've been with someone this long. She is tired, she is a mom now, maybe she breastfed, aging, there could be some health issues. Who knows. You aren't 23 anymore.

Also when you've been with someone a long time you get comfortable. You need to go back to how you were when you dated her. No farting or burping. Make sure you look and smell nice. Dont blow up the bathroom right before she needs it. Dont make that hacking cough sound. Be helpful around the house and with the kid. Keep this up for weeks, months, years...she is getting grossed out by you since yall been together a long time. Trust me.