Hi, again, Nancy. Determining the layers of shingles is easy. Look at the edge of the roof right over the eave and facia board. If there are 2 thicknesses of shingles, you have a one layer of shingle roof. If you have 4 layers, it has been reroofed once. When you start to shingle, you lay one row with the up edge down for a starter course. Over this goes the first layer of shingles laid in the normal manner, thus the 2 layers on the edge.
I would sure suggest that you contact your homeowners insurance agent. They may pay for most of your water damage, including inside the house. But you have to file a claim and get an approval before the work is started, other than "first aid" to minimize/mitigate future damage until the work is completed.