13 weeks today.. depressed, can't eat, tips

I am 13 weeks pregnant with my 2nd child. I have 1 biological girl 6 years old and 2 step girls 3 and 4 that I take care of all day by myself. My 6 year old lives with my parents because that's where she's happy at and she does better in school there. I take care of the 3 and 4 year old all day every day by myself. My fiance works from 8 in the morning to 8 or 9 at night. I just feel like I'm doing everything here alone and I will still be alone when the baby is born. Seems like I'm just not happy with my life. I haven't been out my house in almost a week. I don't have an appetite like I use to and I just want to cry all the time. I get overwhelmed to easy I know but it is hard to be a stay at home pregnant mom. I feel like I'm failing at everything and i just want to feel better so if anyone has any tips for me please share. I just want to feel better and its dangerous for me to be depressed while pregnant because i can miscarry so easy. Please share your tips. I need help and reassurance.