hurt her heart

What is my post-breakup jerk quotient? The history:
Lesbian couple, ages 26 (me) and 35 (Jane). Dated for a month or two, after which I sprung a break up on her, due to feelings of ambivalence and also drama going on with a best friend who wanted to date me.
After a few months of trying to date my friend, I found myself consistently missing Jane. I called Jane up, we hung out, got back together. It lasted 10 months this time, and I decided to let slide the things I didn't like about her, because there was so much I did like. We lived together, it was a disaster. We fought a lot. I questioned our compatibility consistently from month 3 or 4 onward. We tried therapy. It helped a little, but I didn't feel committed enough to work through the issues we had. She convinced me I needed to try harder, that I was too idealistic and giving up too easily. I tried breaking up with her a few times, she always had an easy time talking me out of it.
Brought up breaking up with our therapist, who said Jane had to really take it seriously when I expressed a desire to break up. A couple of weeks later it happened, I broke up with her, and was terrified of losing her but knew I didn't want to continue anymore. Cried for two days and then surprised myself by feeling really over it. Miss her here and there, but overall know it was completely the right decision.

The present:
Enter Lindsay. Knew her casually while I was dating Jane, but never actually took her up on the offer to email her because I knew I had a crush on her, and it felt like cheating on Jane. Ran into Lindsay about 10 days after breaking it off with Jane, sent her an email, hung out. After the first hang out I realized I really liked her, and after I kissed her on the next date I told her I wasn't ready to jump into anything. That I wanted to take it slow. Not happening. We've been seeing each other 3 or 4 times a week, it's hot and sexy and really fun. We haven't had sex yet, but make outs are intense.

The problem:
I feel terrible for Jane. I know I broke her heart when I broke up with her. I think she wanted to be with me forever, and while I made it clear through our relationship that I wasn't ready to think on those terms, I think she still hoped. If she knew I was dating someone again already, someone who I really like and can see getting serious with, she'd be devastated. A friend was frank with me today and told me she thought I was moving too fast, that if I ever wanted a friendship with Jane I was throwing it away, and that she worried I was using Lindsay as a rebound. Therapist also voiced the rebound concern.
I don't think I'm using Lindsay to distract myself. I had wanted time alone, had wanted to date many people casually, had wanted to focus on some friendships. I still want time alone and friendships, but even though I tried to keep Lindsay at a distance and take it slow, it feels like too much work when all we want to do is hang out with each other.
Mostly I feel bad for Jane, feel guilty about moving on too quickly, and maybe feel slightly worried that things are moving too fast with Lindsay, but don't feel like slowing down. I know that would be the best thing to do for Jane, and I feel like a jerk for not empathizing with her more, or being more concerned with how all this would hurt her. I feel callous.

Tl;dr (even though I don't know what that stands for):
Broke my ex's heart, and jumped into something 2 weeks later. Feeling like a major jerk for moving too fast too soon.

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