Technically solo parenting

My story is I am self-employed. My partner comes home once a week if that because sometimes he is away for 2 to 3 weeks at a time and then he is only home one day and then goes back to work, I work for myself which means I have to put my five month old into nursery three days a week. I have to work solidly for 10 to 11 hours each day for those three days to be able to pay the bills, I don’t have any trustworthy immediate family in the area and I do not have many friends and none of them would baby sit, how do you find the time to go to the gym? How do you cope being by yourself? I am struggling being alone and I am struggling with motivation to be more physically active, I want to I just have no drive, any advice would be great. Thank you for your advise in advance.