2rebecca. For sure, the OP's DH cannot stop her having daytime company. If however, as has been suggested, he is a contoller, he may be making it difficult for her to build up any kind of support network. It's a subtle process ime. My ex-H managed to manipulate me into believing that my mother was trying to 'take over' and that she should therefore be kept at arms length. I was young, vulnerable, quite panicked about having a new baby, and he was 11 years older than me. I just wanted to keep 'our little family' together, didn't trust my own judgement at the time, and lacked the confidence to tell him to fuck right off.
OP Please come back to this thread whenever you can and keep talking; you'll find so much support here. I know it's hard to hear, when posters on an internet forum call judgement on your relationship. Only you know what the inside of your relationship looks like and it's possible we've called it wrong. Nothing can prepare you for life with a new baby and perhaps he just has ill-informed ideas about how he perceives it best to deal with things.
There are just a few things you've said that are raising a red flag and it is for you to mull over whether your DH has traits that you're not comfortable with. Please be honest with yourself. If he's isolating you from your mum, is he doing similar with your friends? Is he supportive of you getting a few hours away here and there to catch up with friends for example?
I don't believe any new mother truly knows with any confidence what they're doing in the first few months (years?). We all just try to muddle through with only our maternal instinct as a guide. You sound like a lovely mum, and it worries me a bit that your DH seems to be denying that instinct.
I really wish you well x