Did any of your babies go through this phase at 7 months or right around there?

My son has recently started doing this thing where he arches his back and tries to buck out of EVERYTHING... when I'm holding him now he just arches his back and kicks me HARD with his feet and even when he's on the floor rolling around he'll roll onto his back and do like a back bend and arch his back really far... it's getting to be a problem. He is constantly doing it and last night I was feeding him in a bouncer (i know he's too big for it but it's all I had at my mom's house to put him in to eat) and as I was getting more food on the spoon he arched his back and sort of twisted and tipped the entire bouncer over! Thank GOD I had fast enough reflexes to catch him before he fell on the floor but why is he doing this? Is this just a phase that babies go through? My husband and I have both had SEVERAL close calls with almost dropping him while holding him because he just really fights it and squirms hard and arches his back and tries to buck out and he'll throw himself completely backwards to the point where I"m scared he's just going to flop right out of my arms!