SAHM lonliness

I’m really grateful I get to stay home with my daughter but man some days the loneliness and isolation just kills me. My partner works long hours 12+hr days, 6 days a week. And man, it’s just hard. Just me and my 5 month old daughter all day. Realllly dreading putting her in daycare at some point but I really don’t know how much more isolation and loneliness I can take. Is this selfish of me?