Hate when I don't know what to do

Aiden is in bed crying.

I try to help calm and sooth him when I can - and he was calm when I put him to bed (a few quiet whimpers). He keeps crying and saying mommy - but I haven't gone in because it's calming down and more time is passing between the crying.

Why is he upset?
He wants M&M's and doesn't want to go to bed.

I give him M&M's when he uses the potty. He used the potty and I went to get his 4 M&M's and he got upset because he wanted to get them. (Mr. Independent!) I tried to give them to him and he wouldn't take them. I told him to take them or I was eating them. He didn't take them. I said lets get ready for bed and he refused to come out of the bathroom. I ate his M&M's - picked him up and carried him into the bedroom to get ready for bed. He cried - I got him dressed - he cried - I read him 2 stories - he started to calm down so I read him another story of his choosing. He said he wanted M&M and we talked about why he gets M&M's (for going potty - not for crying). We go to get his M&M's and he again refuses to take them from my hand. I put them away - take him back into the bedroom and calm him down and rock him and then put him to bed.