Are Cruise ships overcrowding the Caribbean?

I have finally booked my holiday for April and I am off to Antigua for 11 nights at the end of April.   I have been to Antigua once before when I was on a cruise around the Caribbean.  It was one of the Islands that really stood out for me and wanted to go back to see more of the Island. 
We are staying on the east coast of the Island but have already said we want to travel to St John's one day to look around the shops.  St John's is where the ships dock in Antigua.  I can remember when we were there that there was only the ship I was on and another ship in port so St John's wasn't too crowded.  St John's is only a small Harbour town and I can't imagine how packed it would be with say 4 ships in port.  I have found a website that tells you how many ships are in port on which day.  I certainly plan to use this site to work out the best day for my shopping trip to St John's.  When you are on a cruise you don't really think about the locals or people staying at a land resort visiting the towns and how busy they will be.  Are the ships getting too big to have more than a couple of ships in port at one time?  I think they are.  I think however much the tourists help the Islands in the Caribbean with them spending money they are spoiling these lovely Islands.  I was lucky enough to be on a small ship when I cruised the Caribbean and there were never many ships in port but I have heard stories about how over crowded some towns have been with the amount of ships and this could ruin the Island for you. 

I am planning on visiting St john's when there are only one possibly two ships in port if this fits in with my dates.  Have you been on a Caribbean cruise and did you find the ports too crowded?