Is it normal to feel sad , weaning from breastfeeding

So I wrote a coupe of post About my baby not taking a bottle and I was stressed because I have to return to work October 12th. But anyways he finally took the bottle ! And it was the asymmetrical nuk nipples he likes . But anyways once he started taking the bottle I haven’t gave him the Breast. I do pump though and give him formula. But it’s been 3 days and I’ve been sad & idk if it’s because of hormones or me wanting to keep ebf. I finally gave in tonight because my breast get sooo full now and I pump like 4oz out of each boob ! He had latched right on and seemed so at peace lol and I miss him not being so fussy because of the transition to the bottle . Have any of you ladies dealt with this ? Like the sad feeling and feeling like you’re failing your baby . I do give him formula as well since I know once I start work my milk supply and Will decrease and I want to get him used to it . I just want to stop pumping and thinking about nursing all together . How long will it take for my milk to dry up ?