Apple - Can I still use my own apple ID with its asociated credit card when I'm in a family sharing family?

No. Any apps you buy with your Apple ID will still belong to you. If you leave Family Sharing other family members will lose access to the apps (Mac OS & iOS), movies, TV shows and music that you own.

Any family member's purchase will be charged to the credit card of the Family Organizer. Gift cards can be used by a family member and they will be charged before the family organizer's credit card. Family Sharing will bill the family organizer's credit card even if other family members have a different credit card on file.

Here is a link to Apple's own support document on this.

I have a workaround: What we have been doing is we have our family account under my sister's credit card. However, the individual members of my family buy Apple Gift cards. This is credited only to the individual family member's account. I usually buy mine at the grocery store, but you can buy them online as well. A little bulky but it works.