I don't feel comfortable giving him formula just yet
There's your answer babe!

If you don't feel comfy, don't give him any formula.

You sound like you are doing a fantastic job...he is getting stacks of BF and solids......and he sounds like a happy little button.

My youngest (Lexie) is a tiny titch and is in the 5th percentile for height and weight. She has just started crawling and has dropped off the charts. BUT she is thriving and happy and placid and giggly and peachy in every other way, so I have stubbornly refused to see this slightness as a red flag.

Easier said than done, I know, but follow your gut. If you think he is doing well, then chances are he is.