So my H walked out almost 3 weeks ago. I got the 'I need space and time', 'I don't know who I am any more', ILYBINILWY, and that being married to me is stopping him from doing all the things he thinks he's never had a chance of doing (including pursuing other women).
That is classic wayward speak. Meaning it is indicative that he is having an affair with, likely, just one woman. He may insinuated he wanted to "pursue other woman" but that was merely to protect the one he IS dating.
If he's having an affair it's also unlikely that you've been doing everything wrong the last few years. Other than likely burying your head in the sand (and not investigating the truth about your life and busting him), it's impossible to be married and act normal with a wayward. If you are nice...it's your fault for being nice. If you are mean...it's your fault for being mean. You can't win because everything and anything you do is turned around by the wayward to rationalize and justify their continuing their affair. I know this is little consolation but his affair is about him, his failures as a man and husband and his lack of coping skills and very little to do with you.
Don't confront your husband. Act naive and find out who he is dating. He said he wants space (which is certain code for "you are interfering with my good time and I want time with the OW to figure out what I want to do". Gather solid evidence BEFORE you confront him (and her). Once it's out in the open...then you distance yourself, GAL and 180 him. It is not healthy for a woman to be around a wayward husband for months (even years) on end. See a doctor and consider an anti-depressant.
Take care of yourself
The internet is 90% complaining and entitlement and I hate it because I deserve better!