Frekkles, I have got DS off to bed at last.
I just wanted to echo what others have said.
Don't give yourself a hard time about your ex. You have to work through your own grief at that relationship not working, have to establish some kind of new, distant relationship with your ex, and have to try and adjust to an unexpected pregnancy. That's more than enough for one person to cope with. You cannot shoulder someone else's grief, no matter how much you might feel you should.
What I was trying to say earlier was that maybe hiding the pregnancy is contributing to your distress; I know that actual events are often far less terrible than I think they're going to be,and after putting them off for ages I think I should have got on and done them sooner.
People will have to know, your bump will show and so will your beautiful baby when (s)he arrives, so you might as well tell them now than later. If you're usually a gin and fags person, they may well have noticed. Loads of my friends smirked when I said I was pregnant, as they'd spotted my inhabitual teetotalling.
Will your housemates throw you out when they discover your pregnant? If they do, they're not worth sharing with. That's the very worst scenario, and even then you can find other accommodation, alone or with more helpful housemates.
Pregnancy is always a time of huge uncertainty and questioning, even if it's planned and takes place in a settled relationship, and to have all these question marks about other people's feelings and reactions can only make that ten times worse. What's vital now is that you get yourself into a position where you have settled, happy accommodation at least until the baby is a few months old, with supportive people around you, and you can then focus on you, your wants and needs. Once you've worked them out, then you can build on your relationships with others. This isn't selfishness, it's the minimum requirement for you to ensure that your baby and you start things off in the best possible environment.
Where are you? I have a vague feeling you're in Edinburgh, but don't know why. I'm from there, will be there over the Christmas period if you want a chat over a Ribena (!). (If you're in Hertfordshire and I've got it all wrong, ignore me!)