about 6months ago, i was using boots monthly contact lenses, and they kept tearing constantly. i ended up swapping to Bausch & Lomb monthlys as these are made of a slightly different material, so are thicker than some lenses. I am also on a scheme with boots, so that if i tear a lense, they give me a spare one to replace it.
youre eyes may be dryer if you are wearing your lenses more often. you may find switching to a different solution might help ie one aimed at preventing dryness. i have just started using the Complete moisture plus solution, and it is so much better than the solution i was using before.