If your losing on AJ it's most likely the way your playing. To help I really would need to know how the people at the table are playing... so I'll give my suggestions like this:

If people are bullying pots~ I would call possibly depending on bet or check if in position to. If top pair you should bet a decent amount i'd say a bet you feel shows you meen business but aren't ready to risk it all ( meaning "Leave yourself Outs!" ) If you had a pair on Js and a higher card appears and the one calling/checking bets he obviously hit a higher pair (so fold). If not check or slow bet the rest of the way through.

If people are playing relatively tite~ You have to bet a little over the Blinds, by doing so many of the players hoping for flop options will fold out leaving thoughs who might call. If called and flop shows and it doesn't hit, check and see what oponents do. If a bet is placed you need to fold as you are now hoping for a catch. If checked through either the player has pockets or high pair and is fooling you or they really don't have anything yet. In these casses if unsure check all through and/or bet small call small, if ever re-raised and you don't have anything or top pair I would generally suggest folding.

These are just a few new things you could try, maybe it's not your style but it's sometimes good to try new things.

Best Of Luck