Weening off breastfeeding to just formula

Decided to start to ween my 15 week old baby off of the boob & give more formula. I’m pretty sad about it, & it is breaking my ❤️, but I️ can tell that my milk is starting to not be enough anymore. He got 8-10 oz of formula a day when I’m working & I️ usually nursed him when I’m home, throughout the night & before work. I’m not sure how long I’ll be able to not feel guilty & saddened b/c I️ feel like I’m letting him down.

Any other moms done this & felt like me? I️ really need support today 😕😕