Oh my god... I feel your pain!
I spend half the year in the UK and half the year in the US, with my girlfriend and her husband. In the UK, I have an unusual setup. Check this out - I live in a 600 sq. ft studio, with my ex boyfriend. No space, no privacy, no separate rooms. If I want to skype with my GF, he hears all of it. But... no rent, either
In the US, like you, I moved into the spare room of my GF and husband's apartment. It's a full house. Three adults, one toddler, two dogs and three cats. In a (very messy) two-bed, one-bath. Agh.
Their bedroom has a king bed, turned sideways, that they share with our toddler. For some reason, our toddler adores me and the inevitable recently happened - she wanted to start sleeping in my bed. Agh. I've managed to suffer it only twice so far and I'm hoping that is the end of that fad. My room has a double futon that sleeps either myself and at least three of the five pets who want to take refuge with me.... or myself, refuge pets and girlfriend, when she sleeps in my room.
Thank God I'm in a v and not a triad, because I could not cope with husband getting in as well. Though he often does; usually when we're trying to work, until he's kicked out. Double agh. My GF asked me to sleep in their room once, to be 'as one'. Myself, toddler, girlfriend, husband, two dogs and three fricking cats. All of their clothes all over the floor (and dresser and cat tree and table). Mess everywhere. Luckily, toddler woke up, started crying about me stealing her bed, and I've had a get-out-of-jail card ever since.
Like yours, my room has also become The Room. It's our office and laundry room too. Though my gf doesn't sleep with me every night, she miraculously manages to create an ungodly mess whilst lying on my bed looking sweet on a daily basis. Our toddler follows suit. I am a writer, also, and I understand the need for personal space. Whether that's a writer thing or not, I don't know!
My gf's husband does not understand the need for space. He turns the washing machine on when I'm working. He leaves his dirty boxers on the bathroom floor until the pile he builds covers it. He gets into bed with us in the middle of private moments. He even admitted that he went through my underwear drawer last time I went home. (wtf).
If my gf needs space, she'll disappear. You'll suddenly look up and realise she's not there. You'll find her in her own room, with the lamp on, reading a book. I swear she doesn't even read it. The pages are most likely blank. But it's her way of saying... "fuck the hell off, you house of crazies, before I bury you under the patio".
When I need space, I'll sit on my bed and play guitar.
So, possible solutions to pick from:
- humour: call yourself a hermit, poke fun at yourself, as it can be easier on your partner's feelings. then use it as a code phrase - "I need a little hermit time; do you still love me? ~endearing face~"
- rules: they go out on a certain day each week and leave you in complete peace at home. It gives you a day to look forward to and helps them to learn to respect your need for space.
- basket system:
My girlfriend and toddler are messy and won't change, no matter how much I beg, persuade, negotiate, order, nag, entice, cry... so I have a basket for each of their stuff. I dump all their stuff in their basket and close the lid. When it's full, I dump it on their bed to sort out. (I took a harsher stance with husband's dirty boxers and said that if he leaves them on the bathroom floor one more time, I will actually tie them to his car with pictures of his face. He cleaned them up the next morning. hahahaha.)
- separate office:
There is something to be said for feng shui. Not only can it be hard to work where you sleep and sleep where you work, but when other people's mess interferes, it can be impossible to function. Can you make their old room your work room? Or screen off a section of the living room? Or find a nice coffee shop?
- separate bedrooms:
This is the best solution, I feel. You could have a rotational sleeping arrangement where you all sleep alone, as a couple, as a triad, on different nights of the week. Or they simply go back to sharing a room and you sleep with them less.
- how to communicate:
I find that the best way to talk about sensitive issues like this is to shift the blame onto yourself as much as possible and remember that they love you and wanted to help you out by accommodating your love of cuddling. Experience is the most valuable learning tool. You made a mistake. You thought you would love it, but you don't want to be a grumpy housemate all the time. You want to be a happy, likeable partner who isn't snappy. You have tried it and realised that it's not working. How about that?
In short... personal space is extremely important and everyone needs different levels of it. It can be the hardest thing in the world to hear that your partner needs to be away from you - even if it's only for a few minutes. Especially if that request is delivered snappily. I think the best thing to do is sit them down, explain your feelings, tell them that you love them and work out a solution together.
Good luck and let us know how you get on!