I'd like to try to help if you are waiting...
This is not my answer. I would love to chat with you if you have time later today. I'm a professor/researcher/counselor and am free today EDT between now (12:50 and 2 p.m.) and then again from about 3-6 EDT. I will keep checking back. For now, I'm going to just get a few thoughts together and write them but again, this isn't really an answer but a start. I do hope we can chat later! :-)
First, it seems like you may have questioned leaving the 5-year relationship after this recent 20-month one broke up. However, you write about the manipulation and lies. Maybe I'm reading into it, but I applaud you for leaving that regardless of whether or not you were to get into another relationship. That one was not healthy, and you do not deserve to be lied to or manipulated.
Thanks for getting back to me - the chat feature was not working yesterday. I am in the UK so 5 hours behind, it would be good to chat soon. I don't really question leaving my 5 year relationship (I had got to the point where I hated him) but I came out of it with low self-esteem for putting up with him for 5 years, not trusting my self and believing that nobody else could love me and it now feels like that is true.
Sorry Uk is 5 hours ahead.
I will try and check back at some point.