Napping Woes

For the last couple of months Andrew has had a hard time napping. He would need to be held until he fell asleep, and then we would put him in his crib. But he would only sleep there for about a half an hour. Then we would go in and have to pick him up to get him to go back to sleep. So I ended up holding him for an hour while he finished his nap, I got a lot of reading done in the last few months.
Last week we decided we had had enough. We were going to start to train him to go to sleep on his own. He is able to go to sleep on his own just fine at night, but not at naps. So we have been using the Ferber method where we put him down and then we "progressively wait" until he falls asleep. That means we let him cry for about 3 min, check on him, leave, let him cry for 5 more min, check on him, leave, let him cry for 7 min....
Needless to say, this has been a tough week. But we did find out we were letting him sleep too long at night, so that is probably the reason he won't sleep longer than a half an hour. We are still working on it, but it does seem to be getting better. We can't wait until he can take a full nap all on his own!