5 1/2 Month Old Stopped Sleeping Through The Night?

My 5 1/2 month dd started sleeping through the night at 8 weeks. Once she reach 5 months, she has now started waking 2-3 times a night. She is not crying. She usually has her feet in the air trying to grab them when I go into her room. She's babbling loudly and yelling. Not really upset. It is loud enough that I cannot sleep. I was going in and rubbing her cheek and shhh shh shhhing her and she would go back to sleep for a couple hours. The past couple nights I have started nursing her again which gets her to sleep another 4 hours or so which is better then waking every 2 hours or so. She doesn't seem in pain so not sure if teething is the cause. Has this happened to anyone else? I am so tired I feel like I'm going looney. I work full time so no sleep is rough. Help!