OMG. I don't know what to say but feel I should say something.
Please listen to people previously who have said it will get better - possibly a lot better. I know you won't believe it and I bet you are sitting their now thinking how can people say it will get better when they're not living my life. But believe me, people do understand and have gone through the same things as you and come out on the otherside - scarred perhaps, but better and stronger for it.
I found the saddest part of your post the fact that you have no one you can talk to about this. I can sort of relate as I do not have many friends and always found it difficult to forge good friendships. I have, i. The last couple of years rectified this a bit and you can too. Can you get out and mix with people a bit more? I know that is possibly the last thing you feel like doing right now, but it really helps with meeting people.
Evening classes, parent groups, social clubs anything really - hell why not even place an ad (daunting perhaps, but you will b surprised in the number of likeminded people who want company - just weed out any weirdos!).
If you are really finding it hard to cope and feeling suicidal then please see your GP as others have suggested. They can help you and put you in touch with the appropriate support. Remember, you do not have to be alone - even if you think you are.
I'm sure you are a great person and mother. You are not letting anyone down or failing. On the contrary, it sounds like you are doing an excellent job under the circumstances.
You mention you have met a new lovely man. Good for you and I hope that works out. Don't assume your circumstance will scare him away - he was obviously attracted to you so you are desirable. That said, don't put all your eggs in this basket either - you need to be a little bit selfish too (not too much) for yor own sake and for your chold.
Good luck. Things will improve - illulook forward to read the future post about how great your life has become - thnk positive!