Go for safe and repent anyway...especially if it makes you feel bad. this of course includes your promise not to do that again...in the meantime you can check whether it really was a sin or not. even when something is permitted, it may be a bad thing so repenting is always useful.
about asking forgiveness about sins without a sin in mind I do not know.
but if I may share how I think about it...I think yes.
We humans commit many sins sometimes small, sometimes big. sometimes in full consciousness, sometimes unaware at that moment. It is impossible for us to remember every single sin we committed. Surely Allah still gives us the chance to repent for all our sins, even the ones we cannot remember. So my logic says, yes Allah will forgive those sins when repented.
But again, this is my personal thought...So I am not sure.
like many times repeated here, the situation is different if someone else is included in this. If you have wronged someone else, this of course will not be forgiven just like that.