I fed DD for 9 months even though I was pregnant with DS, who was born 3 months after I sttopped feeding her.
I tried so hard to feed DS but he hated the breast! I has so much milk I could fill a b ottle off one side whilst feeding him, he fought the breast and arched his back, but took breast milk like a dream in a bottle. I tried taking milk off first, but it made no difference. I fed him like this for 8 weeks and then gave up and put hiom totally on the bottle, I had boobs like footballs for 8 weeks so was glad to give up.
I then went to Spain on my own with them, age 15 months and 12 weeks and wished I'd persevered as I ended up having to take, formula, bottles sterlising stuff etc, a real pain!
Don't feel guilty, do what's best for you. DS is also the healthier of the two, not been to the doctors in 10 years, DD has asthma, a nut allergy, and used to have excema