I'm not in an episode iv never been happier people just don't like to admit people can change
No. Your last severe episode was only four months ago. For three of the months since then, you've been in an intense new relationship that you're hiding the extent of from your support team because you know they will have deep reservations.
You're idealising your partner and his future behaviour even though you're hiding a great deal of serious information about your mental health, current contraceptive status and history of having children removed from you because you're trying to trick him into having a child with you without discussion because you believe it will mean he then 'can't' abandon you.
You are so attached to this new relationship that you feel you would commit suicide if it ended, and in the very likely event that it does when your boyfriend finds out all the stuff you've been hiding, you will then likely have another severe self-harm crisis.
If it's truly all good and your mental health team who are professionals who will presumably understand your condition well and be capable of assessing whether you can change then if you tell them everything you've said here, they'll back you up and support you. But if it's not all good, telling them may well save your life, avoid a serious trauma for your boyfriend and prevent yet another child ending up in the care system.
Do the right thing, not the thing you want to do.