This has happened to me a few times recently and I am utterly confused as to what to do, preflop, flop, everywhere... UTG 39/7/4 over 58 hands and MP is 32/11/1.8 over 100 hands.

Full Tilt No-Limit Hold'em, $0.25 BB (6 handed) - Full-Tilt Converter Tool from FlopTurnRiver.com

MP ($26.15)
CO ($49.95)
Hero (Button) ($48.85)
SB ($28.40)
BB ($5.35)
UTG ($29.45)

Preflop: Hero is Button with J, J
UTG raises to $0.50, MP raises to $1.85, 1 fold, Hero calls $1.85, 2 folds, UTG calls $1.35

Flop: ($5.90) 6, 9, 2 (3 players)
UTG checks, MP bets $5.90, Hero folds, 1 fold

Total pot: $5.90 | Rake: $0.25
Am I essentially set mining with J-J here? No way it's good on that flop facing a PSB, only thing I beat is 10-10 and maybe maybe a wild played A-K? Idk, I suck.

I think for the most part you are set mining here. Although it is possible that the middle position had a hand like AKdd preflop. So there for on the flop even if we are ahead we are still a slight statistical underdog so this this is a tricky spot. One thing we know is that by his bet on he flop that he wants to take the pot down right there. Is that because he fears his AA,KK or QQ might get outdrawn or Is he making the semi bluff with 2 overs and the nut flush draw? Guess this depends on your read of the player. Without alot of info on the player i think this is a clear fold. You can find a better spot then this to get the money in.

Edit: Also if you suspect that he has AKdd, then i would flat call the flop, and push the turn if a scare card doesn't hit. No point in re-raising on the flop, He is never folding that flop with AKdd. However if you were to push on the turn, You are getting some fold equity, however players at this stake might make the call anyway, which we want cause we would be a clear favorite at that point.

This is why JJ is considered one of the, if not the most difficult hands to play in NLHE. It's very possible the MP has a strong holding here like AA, KK or QQ but its just as possible he has AK suited or trips. As you played it I think a lay down would be best play but depending on your image a re-raise is possible on the flop but be careful. I would have re-raised pre-flop to about 4.50 or so and put the pressure on the other 2 players. If I get any action after the 3-bet then I'm done with the hand unless I hit trip J's on the flop. Obviously with the 3-bet pre-flop I'm looking to take it down right there since JJ after flop is usually scary as hell.

I believe MP could be reraising there with a massive range of hands, the raise before him was minimum and I doubt he actually has a proper 3 betting hand. On the flop, he only has one call behind him, and one infront. UTG checks, villan bets to hero because hero showed no signs of a super strong hand (you flat called with position, mostly screams 'I have a mediocre hand, would like to see flop'. I reraise here 80% of the time.

mp fires pot into a suited slightly conn. board, doesn't seem like air. I don't raise this flop, if you're putting a raise in do it pre.

I think at the very least you have to call the flop bet then re-evaluate the turn.

Our prob is taking JJ three way into this flop.
If we were heads up, I think we could pot these flops and make $ over time.
Three way with this action PF, I think we're beaten.