rotator cuff injury

Hey all, I've been swimming my whole life including a couple years on the HS team. After that it's been hit and miss, but I've been consistently in the pool the last 4 years and have been happy with my progress. Just the other day I was doing some lake swimming and the last 1/2 mile I felt a pull up my right side. It wasn't debilitating at the time so I kept swimming, plus I was in the middle of a lake so I kind of had to keep going. Everything felt fine until I got in the car and drove around a bit, then the shoulder got very sore and I couldn't raise it over my head. The next day I went to the chiropractor. He said it wasn't a tear, but the rotator cuff is strained and causing me problems. He did wonderful work and I'm very happy with him. He said it could take as long as 6-8 weeks to heal. I'm sort of resigned to that fact even though I'd signed up for a series of swims this summer that I won't be able to complete if this injury is that bad. This is a long story for a short question. How do I avoid injuring the rotator cuff again? Is it rotation in the water? I've been conscience of pulling from my lats in the last few weeks so as not to strain the shoulder too much. I've got a 5 mile swim in about a month if I can do it. How do I do it without injuring the shoulder even more? Thanks