Why does everyone keep calling me?

I've had a very frustrating few days this week and lost about $1000. Here's a major problem I keep running into:

Everyone calls my pre-flop raises.

Here's what I raise on: Pocket pairs, suited connectors, and any 2 split cards 10 and above (10 J, J A, etc).

I don't bluff with preflop raises, at all. Yet everyone calls me without a second thought. This rarely occurs when any other player raises. When another player raises, they'll average 2-3 callers on a full table, but when I raise, I average about 5.

I raise the same general amount that everyone else does pre-flop. Granted, when I raise, I like having at least a few callers to get some value out of my cards, but with 5 callers per raise, alot of people see the flop against me with complete and utter crap...and they hit.

It's just really frustrating to have a guy with 7-5 offsuit call my $10 raise in a $1-$2 NL game, and then hit two pair or an open ended straight on the flop just to suck me out further down.

Am I doing something wrong?

Should I tighten my starting requirements for a raising hand?

Loosen them?

Why does everyone call me?