New to stud, help on this one

[steviej1717]

I have rolled up 3's and another player has 3 diamonds showing on 5th.

We are heads up due to 4th being capped by me.

He catches another diamond on 5th. His door is an A, so I am not sure if he has the flush or split A's (possibly rolled, no other people had one showing on previous streets).

HU we capped 5th and 6th.

Obviously jam if I boat on the river, but what if I brick?

FWIW, this was 5c/10c on pacific, although this guy did seem like he knew what he was doing as far as I could tell.

Apologies if its boring or routine, I just started playing stud online about a week ago.

Thanks.