Congratulations on all the weight you have lost! It's a really good sign that you caught the gain at 20! Personally, I had lost from 193 down to 142, then gained back up to 193, then had 2 babies and ended up at 236! So you're in pretty good shape IMO.
It is hard starting back up; I found, for me, that just jumping back in with both feet and committing to it worked well. I kind of just did it, and the motivation followed, then it went away, and came back, and went away again (I don't know where it is right now, but I'm keeping at it even with no motivation whatsoever). The good thing is that the commitment stayed even with the motivation ebbing and flowing. I also try to just look at the next 5 to 10 pounds, looking at the whole thing got way too overwhelming.
Well, hope that helps, it felt rambley!
(spell check is telling me rambley is not a word, but it should be)