Ill try and dig some sites out for you, unfortunately, my coach has just left on a holiday, and I’m sure he would know of some. I would advise that if you are serious about improving that you employ a swimming coach at the pool where you train. You would be surprised what a couple of hour sessions would do, it shouldn’t cost much either.
Without seeing you in action, I can give you a couple of pointers in the meantime.
Firstly, as I said before, I would place money on your legs dragging you down. To correct this you want to work on strengthening your kick, but also think about your head position. You didn’t say what stroke you are doing, but whichever, do not raise your mouth any higher than you need to to breath, and also move you head without moving the rest of your body. If you are swimming freestyle, your eye line should be just below water level for the majority of the time. Breath out with your head in this position, so that you head is to the side only to inhale, which reduces the timeout of position.
Also, if you lift, I wouldn’t be surprised if your shoulder flexibility is somewhat restricted. This causes the arms to swing round, rather than through on freestyle, and makes the swimmer “snake” through the water rather than moving in a nice forward motion. Work on keeping the elbows high and pulling the hand past that arm pit than continuing to a full stretch before pulling back. Your right arm should move in a question mark shape as it pulls back beneath your body, first using your lats and bis to pull, than your tris to push back.