Another 18 year old who's mother needs to accompany em to appointments here!
Here's my opinion. I believe that you should stop cutting, but in no way is forcing you going to help that. If you have no tips to safely cut, you'll likely do it dangerously (like I did)... so for the sake of harm reduction..
Try to use sharp blades. Dull ones can cause major damage. If you can get your hand on a sharp razor blade, keep it close (you can use the other people's tips on how to hide them, like in your phone case, etc), but PLEASE keep some alcohol wipes with you if you can. There are ones that come in little mini paper packets the size of a quarter, you can easily hide one or two with your blade. Open the packet and wipe down the blade before use.
As for hiding wounds, it depends where you cut.