It’s not easy because it’s a short extract but I’m pretty sure the sense of “déception amoureuse ou pas” is very close to the first translation you did. For a better understanding I would say the global meaning is something like:

Go shopping nearly always results on purchasing for me and at the moment, maybe because of my broken heart – or not – I just can’t help buying everything !

So as you can see, it’s very close to your first translation.

If the “Déception amoureuse ou pas” had come at the end of that statement (i.e., “Je peux pas m’empêcher d’acheter tout ce que je vois, déception amoureuse ou pas!”), I’d definitely interpret it as “Whether I’m suffering from a broken heart or not, …” (which I could almost see as coming across resentfully/defensively as “Don’t worry/flatter yourself [my love], I’m a bonafide/proud shopaholic with or without your ‘help’!”).
However, for some reason I can’t explain, seeing it at the start of the sentence helps me understand your dilemma, for I am not at all sure that it couldn’t mean “I don’t know if it’s because of my broken heart or not, …” when appearing in that order.

Regardless, I would simply add “Par” in order to help convey the notion of “because” and avoid the risk of sounding resentful, as follows:

Par déception amoureuse ou pas, je peux pas m’empêcher d’acheter tout
ce que je vois ! C’est plus fort que moi.