Just a thought of something to try, as I'm a novice myself. There are needles meant to be burlier (size 16, size 18, ones meant for denim). This should only be a problem if the needle breaks or maybe has trouble piercing the fabric, not with thread bunching. It sounds to me however that yeah, maybe your presser foot is down if it's stopping up and having thread bunching issues on the bobbin side.
Also I'm not sure how long you've had your sewing machine. I recently bought one from Walmart (brother brand) that had no bobbin tension, at all, it'd just slide around. I could tighten the bobbin tension but only by taking apart the dang machine. In the end I messed it up worse trying, then just exchanged the machine. It stopped doing the bunching on bottom (bobbin side for me) thing.
Again though, my bet is that you didn't drop the presser foot.