new swimmner(sort of) need advice

Hello! This is my first post. I have started swimming more lately because I need a layoff from running to let some injuiries heal. I swam as a kid and some as an adult but I am now interested in getting better and swimming longer as cross training. Here are some questions: 1) Is my back hurting due to bad form or have I simply ramped up pool time too quickly? I have been swimming for about 3-4 weeks and now swim 45-60 minutes at a time.:dunno: I'm in good shape so I don't get tired that quickly but maybe my body needs to get accustomed to swimming? 2) are there any earplugs that really work? I've tried two pairs. One was a wax like thing that didn't stay in long. The other is a rubber thing with a long handle - it's better but doesn't keep all the water out 3) I try to beathe every 4 strokes. Is this good? It gets harder after about 15-20 laps and have to go to every 2 strokes occasionally Thanks, I'd love any advice you can offer for newbies