Johnny Manziel -- JOHNNY RELATIONSHIP??? ... QB Getting Couply with Hot Blonde

Johnny Manziel may be on the verge of GF'ing up ... 'cause the NFL's most eligible bachelor has been out several times with the same hot blonde -- AND POSED FOR KISSY PICS!!!

The girl on Johnny's cheek is Colleen Crowley ... a college student at TCU who was first spotted out with Manziel roughly 5 weeks ago when they hit a Houston nightclub together.

Then, there was the baseball date at Fenway Park ... followed by a booze sesh at a Boston speakeasy.

Now, the biggest clue they're getting "official" ... they BOTH posted kissy pics on each other's Instagram accounts last night (well, she was kissing him ... but he was cuddling her back).

Soooo ... congrats???