Your description of pain with the vaginal opening makes me think a really careful exam is your next step. It sounds like vulvodynia (also called vestibulodynia) should be considered. This condition results in pain with penetration, usually described as a burning or tearing sensation.
A lubricant can make penetration less uncomfortable, but it doesn't make it comfortable.
Another possibility is that the absence of estrogen has led to atrophy, resulting in the loss of caliber (size of the opening) of the vagina. If that's the case, using vaginal dilators may restore size and comfort.
In either case, I'd encourage you to see your healthcare practitioner. Stick with it! I know you can be comfortable and revive your sex life!