Slowing down TPTK to what?

I had TPTK in this hand and got check raised... I slowed down, but when he checked on the river, I put him on a draw. Anyone else have a suggestion as to what this guy was running with?

PokerStars No-Limit Hold'em, $0.25 BB (9 handed) converter

saw flop|saw showdown

UTG+1 ($28.45)
MP1 ($26.50)
MP2 ($36.55)
MP3 ($22.40)
Hero ($11.15)
Button ($6.70)
SB ($37.65)
BB ($22.85)
UTG ($25.90)

Preflop: Hero is CO with J, A.
5 folds, Hero raises to $0.75, 2 folds, BB calls $0.50.

Flop: ($1.60) 7, 3, J (2 players)
BB checks, Hero bets $0.75, BB raises to $2, Hero calls $1.25.

Turn: ($5.60) 8 (2 players)
BB bets $2, Hero calls $2.

River: ($9.60) 5 (2 players)
BB checks, Hero bets $3.25, BB folds.

Final Pot: $12.85

Results in white below:
Hero has Jh Ad (one pair, jacks).
Outcome: Hero wins $12.85.

Only thing I could think of is a diamond flush draw, possibly straight to the J until the river came.

Diamond flush draw almost certainly. I've seen guys play it that way a lot online.

I would assume draw as well, although J10ish would also make sense, he's testing on the flop, then on the turn he picks up a draw as well.

If you call the flop, you've gotta raise that turn bet.

-'rilla