Can we subtitle this one: how to fight blue balls?
Very common, esp playboating. I keep a sponge in my boat. Some (not many) sew their drytop to their skirt to reduce "leakage." (note this can pose a safety hazard, but is generally safe for just playboating) Definitely check all your screws, put duct/gorilla tape over them if you're still not sure if that's source. I find it's usually your skirt. A snug tunnel fits help and your seal around the cockpit probably makes the biggest difference. Short of buying a new skirt, you might try buying some weather stripping and putting a layer around the outside of your cockpit rim. I've found this to help some. I've heard others recommend a bicycle inner tube around the cockpit rim (I've found this to be less helpful).
Most people just learn to deal with a bit of water seeping in and empty their boat now and then. It drives me crazy though.