help !!

So I have a question for you ladies  have any of you tried to get your milk supply back? My son is 3 months old and waS strictly breast fed for a month. When he was breast fed he was fine but now that he's formula fed he has a lot of gas and tummy problems. I feel like I gave up to fast because he wouldn't latch and I was going through a hard time. It's one of my biggest regrets but I'm determined to get my milk supply back. If any of you ladies have tips please let me know. Thank you 😊