Need advice

My son will be 6 months on the 5th when he was newborn all the way up till he was maybe 3 months he would take forever to get to sleep but he has always slept long stretches any where between 4-8 hours. Well the last week or week in a half he has been waking every hour or even waking up  and falling back asleep and waking every 20 mins like tonight he went to bed at 7 than I fed him at 9 and than I went to bed he woke up at 11 and hasn't really slept since. I have no clue why he might be doing this. We did recently sleep train him he use to fall asleep in the swing than when I went to bed I'd feed him and put him in the crib. We have been working on teaching him to self sooth and fall asleep in his crib if he crys more than 5 mins I go in and pat his back. Right now he is on me chest sleeping because at this point I don't know what to do. He is fed changed and I go in and pat him back to sleep than once I lay down he is crying again. Also my so hasn't slept on me since was a new born he likes his space so at this point I'm thinking he wants to be comforted maybe he is teething. I have no idea but I miss sleep any advice or idea as to what's going on with him?