Fetty Wap is doing a complete 180 -- he's now owning up to being the father of Masika's baby after vehemently denying it at first, and he's dropping major coin on her and the kid.

We're told Fetty dropped $20k on baby clothes, toys and furniture over the weekend while out shopping with the ex "Love and Hip Hop: Hollywood" star at fancy LA baby shop, Petit Tresor.

He's come a long way since Masika filed paternity docs 2 months ago when Fetty claimed he wasn't the father of her baby. Our sources say Fetty's now doing everything he can to help out, including taking care of Masika.

No word if they're rekindling the romance or if he's just playing nice with his baby mama -- either way she seemed very pleased at Mastro's last weekend.