Should I go forward with crush during my (dead?) relationship

So here's the deal, First off, yes Im in a practically dead relationship with someone else. Im also pretty certain this other girl she knows I am, even though Im never with her when we see each other. For what it's worth, our relationship has been dying/stagnant for about two months, before I even met this girl, and we're seeing each other fewer and far between. Id wager to say the in limited amount of time I've known and hung out with this other girl is larger than with my gf. Im an asswipe I know. But I still would appreciate some help. Perhaps Im just scared of completely letting go in case it doesn't work out with this girl as I think it could, I dunno. We're on a..."break" (I hate that word so much) but we never discussed dating others and even so I wouldn't, I just want to see if this thing with the other person could lead somewhere. Anyway, whenever this other girl and I have seen each other, granted never alone but do spend most of that time with each other, there always seems to be this connection between us. It's been about four times during the past month. Over the weekend I saw her and we talked, later texted her and told her to let me know the next day if she wanted to go see this movie, with me and other people. I really couldn't ask her out because Id feel bad about it, I just want to get a feel if there's a spark between us. Im scared of ending up without anything perhaps, what can I say. So yeah, she seemed excited just not completely sure because she may be doing something else at that time, but would let me know either way. Since I've always been the one to text her first, literally every time, I took her for it that she would let me know, and she didn't. Just like every other time she's told me she would let me know (but for other smaller things, not particularly going out somewhere). This was yesterday, and as has been the case Im sure she wont be texting me before I do so first. I really dont think waiting for her to do so would do any good because Im almost certain she wont. So, should I? And if so, what should I tell her, I mean we didn't have any concrete plans, she was just gonna let me know. Perhaps she was waiting for me to ask her yesterday if she was going?? And after that, it will likely continue being that way huh? She never wanting to text first. We still had one other minor thing pending she's always telling me she'll let me know and continues to bring it up when we text each other and see each other, but never does. Ever. She does send mixed signals at times, heck perhaps she's just really nice I can accept that, but really it's just the times we look at each others eyes for prolonged periods and smile and laugh about it, talking kinda deeply, when she tells me to come over anytime; But these not texting me first ever wow! Im obviously a bit confused but any help would be appreciated here.