sql runs fast in ssms slow in asp.net

I have been having this problem for a couple of weeks now. The problem is that the query takes 4-5 minutes to run on the website and at most 2 or 3 seconds to run in ssms. Also I found that after I make a change to this query like adding the customerId variable it will start running quickly on the web page but by the next day it is slow again. The query in question is this one: