You aren't stupid. You are NOT a failure! You are a lovely, warm person who put her trust in the wrong man. We've all done it, some of us more times than we like to think about
. It's so painful to realize that someone we love doesn't love us, but it will get better in time.
As hard as it will be, I do think it would be better if you told him to leave now, tonight. If he'd rather be with her, you can't really stop him, you can only prolong the inevitable. Does it really help you to be sitting there, looking at him or hearing him moving about your house? Like a cancer, it's better to get it OUT as soon as possible.
Is there someone in RL, friend or family, that you can call to come over?
If I may; CrimsonDay, please meet Littlefluffyclouds81. Littlefluffy, meet Crimson. Proof that there ARE others out there who have been dumped (God, I hate that word! How about 'not appreciated' or 'freed') and who will also heal in time.