I have been crying about this for days and I don't know what to do...

I have breastfeed and now I just pump. I have been doing this for 5 months now. I raise my daughter alone as my husband is overseas. My daughter is awake often and wants to eat every 3 hours, I have to pump every 3, and somewhere in between I have to find the time to eat myself do chores shower go shopping for stuff we need at the house. I just feel like I can't do all of this especially on my own. I am having a really hard time on weather I should just give her formula or not. I feel like I won't be giving her the best. Is that wrong? I feel selfish for wanting to stop and it make me feel even worse. I just want to do what's best but this situation is making me incredibly sad. I don't know what do do and I could use some advise..