Welcome to the world of being a SAHM and others reading it differently... you are not mobile entertainment, you are not a housewife, a domestic goddess, or anythingbloody else. You are your child's childminder, you're unpaid and happen to be the parent.... you wouldn't expect a full time childminder to bog off away for xdays because they have nowt better to do would you???
You need to define yourself, your role, and lay the law down with what you will and won't accept from your DH in terms of his level of understanding... he's probably a fantastic guy (I hope!) but he doesn't KNOW what you do all day... seriously, sit down and talk, both of you, about what you both NEED when 'worktime' is done - that's when he gets home, until baby is asleep... you both have to muck in, then you decide what you need to do to relax and feel appreciated, both of you. I want a bath, that's all I want, and I do not do housework after 9pm, and neither does DH. For example. We both do long hours.
Your mum's problem is I'm afraid something you can do little about, but I also understand its yet another emotional drain.
You need to TELL friends and family how busy you are, but then you risk becoming a 'mum bore'... its a fine line! If they carry on badgering you, hang up.
Some of my friends manage by becoming old nags, whining matrons, always saying 'wor is me my life as a SAHM is soooo hard' but that just makes everyone want to stab them with blunt pencils (metaphorically speaking), what I do is I don't SAH. I'm out, and my mobile is often out of credit because I can't be arsed afford to top it up. If my friends and family cannot reach me at home (you can also be at home but ignore the phone) then strangely seem to think I'm ever so busy (which I am even if I answer!).
LOVE YOUR JOB, don't make excuses, don't be someone else's idea of a mother. I have more time 'to myself' now, 3 hrs a day in total, no more or less than many full time working people, some days are easy peasy, some fucking hard. However, my friends and family can never phone me and hear Jeremy Kyle in the background a) because its a crock of shit and I'm usually up to my elbows in home made bloody play doh and b) I don't answer the phone.
Long winded... chin up. Don't try and keep up with anyone but your child.