Stay at home mom to working mom

I was able to be a stay at home mom since my son was born until now(he's almost 3) it was my decision to start working again because I know it'll help both him and I both, he needs to be around other kids and get used to mommy not always spending every second with him as he will start preschool in a year and I need a social life outside of being a mom. But I'm having a hard time adjusting to this, I'm used to being with my baby all the time. With my work I applied for part time so I'd still be able to spend a lot of time with my son & I was gonna go full time once he starts preschool, but my job wants me to start full time 7:30am-6:30pm... My son goes to bed at 8 so I'll only have an hour and a half with him... Should I tell my work that I can only do part time right now (but can switch in a few months) or will it get easier for me?