General rules of thumb that are hard to get in much trouble with:

- raise an unraised pot with jacks or better from all seats; add tens and nines in late position

- limp all other pocket pairs from all seats

- call raises (pre-flop) with any pocket pair, as long as there's enough money in play that you'll get paid off when you make a set; i.e. calling a 5xBB raise with deuces is fine if the raiser has 20 times that much in his stack left

- look to hit a set first and foremost; the lower the pair, the more important it is to hit a set. lower than pocket 7s, there's no reason to bet unless you made trips

- If you didn't hit the set but there are no overcards, bet cautiously; you have probably the best hand, but it's as vulnerable as any top pair. That is, two pair still beats you, higher pocket pairs still beat you, etc. Be willing to let it go. If there's one overcard I'd limit myself to one feeler bet and then go completely passive if they stay in the hand.

Basically it seems to me like you are raising too much pre-flop with pairs... they can make more money if you keep more people in and hit a set or boat against the right second best hands. Ideally you'd rather call a modest raise, because the other player is the aggressor and may be more likely to throw their entire stack in the pot, regardless of how much strength you show later.