Am I a bad mother?

Coleson has been sleeping through the night really well. For about 5 weeks in a row, we were sleeping through the entire night. It was wonderful and I was really getting spoiled. Things have now changed. For some reason, Coleson is waking up around 4:00 now. I’m not sure why. I would assume for a bottle, but why is it just starting now. I have tried everything I know to do. I now give him 5 oz with rice in his bottle. I’ve tried keeping him up later, but nothing is working. I don’t know what else to do. Two people have told me that if I let him cry himself back to sleep that it will only take three nights for him to figure out that I’m not coming to get him and he will teach himself to go back to sleep. Well folks, tonight will be night number three and I don’t know if I can make it. Sunday night, he woke up about 4:15 and whined a little but eventually went back to sleep for a little while. That was not the case last night. He woke up at 4:00 and cried for two hours straight. Dennis kept saying, “Don’t get up and get him. Just let him cry.” Finally at 6:00, after cat napping for two hours, I gave him a bottle. It was almost time for me to get up so I don’t think that I messed up what we are trying to do. Who knows what tonight will bring. I guess what I am trying to get at is am I bring a bad mother for letting my 3 month old baby lay in his bed and cry? Is it normal for them to cry for this long during the 3 nights that I am waiting out? It breaks my heart when I go in there and he looks up at me and gives me a big smile. Now I do understand that he is a baby and that they wake up at night, I just don’t understand why we did this for so long and now a change. Does anyone have any advice?