Jordane, your post is very confusing, so please forgive me for asking questions to clarify.
Have you been to court to seek regular access visits? Do you pay regular maintenance? Does she still live at home with her parents? Do you have a job or are undertaking vocational training? You mentioned your parents welcoming her into their home - does this mean you see the child's mother at present? If so, why does she not bring her daughter too?
That aside, the two of you were a parent's nightmare. Did they not teach contraception at school??!! Frankly, if the parents are blocking you, it's really not surprising. Likewise, I understand why your parents blocked her.
If you want to get past her parents, you're going to have to prove you've changed and become reliable and sensible. At the very least, you must be clean, have a sensible haircut, be well presented, not do drugs or drink to excess, have a job and be paying regular child support...or if you're not working you must be undertaking further education or vocational training, attending regularly and passing your course with flying colours.
Never regret anything that has happened in your life. It cannot be changed, forgotten or undone. So, take it as a lesson learned and move on.