Good for you, girl -- you're not 'playing mum', you ARE being mum.
How soon people are ready to go back to work is incredibly individual -- I did 2 mornings a week with my first from 4 months, which suited me brilliantly as it was just enough of a break without making me feel I was abandoning her.
With ds I had to go back at three months and HATED it.
With dd2 I work at home while the baby is asleep (notionally). I should really sort out a childminder three mornings a week, but she sleeps really well, and I love having her around. We have a running joke about her being my 'familiar' -- like witches have, my little creature who goes everywhere with me.
On a completely different thread a few weeks ago someone posted this poem:
Song for a Fifth Child
Mother, oh Mother, come shake out your cloth
empty the dustpan, poison the moth,
hang out the washing and butter the bread,
sew on a button and make up a bed.
Where is the mother whose house is so shocking?
She's up in the nursery, blissfully rocking.
Oh, I've grown shiftless as Little Boy Blue
(lullaby, rockaby, lullaby loo).
Dishes are waiting and bills are past due
(pat-a-cake, darling, and peek, peekaboo).
The shopping's not done and there's nothing for stew
and out in the yard there's a hullabaloo
but I'm playing Kanga and this is my Roo.
Look! Aren't her eyes the most wonderful hue?
(lullaby, rockaby, lullaby loo).
The cleaning and scrubbing will wait till tomorrow,
for children grow up, as I've learned to my sorrow.
So quiet down, cobwebs. Dust go to sleep.
I'm rocking my baby and babies don't keep.
by Ruth Hulburt Hamilton
This sums up how I feel so much I printed it out and hung it on the wall above my desk, to make me feel better about skiving off work to play with the baby.
Go for it, Wellsie! Who cares what your in-laws think? If they're anything like mine, everything you do will be wrong anyway, so stuff them, and do what you and your dh are happy with.