Sleep Training and Teething

DS started STTN (for 8-10 hours) around 7 weeks.  He would almost always fall asleep nursing and either sleep straight through the night or would quickly fall back to sleep if he woke in the night.  This continued until he was 3 months.  At this point, he started waking for night feedings again, which lasted about a month.  From 4 months to 5 months, he STTN again.  For the past few weeks, he has started night feedings again.  I have always nursed him at bedtime, and most times, he would fall asleep nursing.  I wasn't concerned about this habit because he was able to put himself to sleep on the occasions I put him to bed drowsy.

Now, he wakes several times in the night and won't go back to sleep without nursing or being rocked to sleep.  Lots of times, he will wake back up the moment you put him in his crib (he's been sleeping in his crib in his own room since about 6 weeks).  He has been teething for several weeks now, and I don't know if he's going through a sleep regression or if he's waking up because he's in pain and just wants to be held. 

Another theory I have is that maybe it is a sleep regression that is linked to growth spurts.  Seeing as his STTN got messed up after his 3 and 6 month growth spurts, I wonder if that could be the case. 

I didn't think anything of sleep training before and was very thankful that he handled bedtime as well as he did.  Now I'm starting to get concerned that I've started a bad habit.  But if this really is just a problem caused by pain from teething, I'm worried that sleep training will be a futile effort.  I do not want to CIO, but I am possibly open to the idea of Ferber.  I haven't really discussed this with my husband yet and am really in the beginning of my research.  I would really appreciate any advice you ladies can offer, and if you read this entire novel, I appreciate that too!