Try exfoliating and moisturising your skin to prepare it, then when it's dry, cover the worst scars in concealer. Then add a layer of foundation and blend..that won't make them invisible, but it should make them much less noticeable.
Another option is fake tan, the spray on kind, it adds a layer of colour which softens them and some brands actually cover scars up.....although it depends on your skin type. You also need to be really careful and not use it on fresh cuts or scars..which it sounds like yours might be :/. Fake tan could be followed by if necessary a layer or two of concealer/foundation to blend better.
If you want to help healing and make the scars less permanent or less noticeable in the long term, try BioOil...it's really good and even Primark sell it now so it isn't that expensive anymore.
And...I know you probably don't want to hear this, but please don't hurt yourself...it may feel like it helps now..but in the long run it really doesn't. I know its hard to stop...but cutting..becomes addictive and the further down the line, the harder it will be.