Has potty training reverted for any of your children too?

My son is nearly 4 y.o. and my boyfriend and I Finally had our son going to the potty when he felt the need to--for around a week. He was given stickers, we were excited, and then today---he has been to the potty twice. At my urging. Once I even bribed with chocolate and I do not want to do that at all, but, I felt like all progress was becoming lost. So, I went with what would work, and it did for that once.

What is happening? If this has happened with any of your children, how do you get them back on track?

He also Hates wearing underwear, and wants a diaper back on. How do I get him to want to wear underwear instead of diapers?