My past as a catfish who extorted people

I want to start off by saying I obviously feel horrible, hate myself, etc. This is going to be a lengthy confession so if you manage to read it all I can appreciate it.
In 2012 I discovered both *mod edit* and *mod edit* messenger app, I was 15 at the time. I was a shy kid so it started off as just a fun way of meeting people, chatting to girls or just joining in some random stuff. All was ok until I discovered an app called *mod edit*.
Basically, what I did was I got this stupid idea to create a catfish account. Now I had not been very experienced sexually at this time, so just seeing women nude was exciting. So I would go on google images and search for a 'macho' looking guy and pretend to be him, I would advertise my kik on omegle and would get some messages from girls.
It started just with some harmless raunchy talk or pic sharing, nothing too bad (bra, cleavage, etc) but it soon moved to where girls would send nude pictures. To skip ahead, I eventually developed this awful, horrible thing where after the girls sent me these pictures I would say 'I will only delete these photos if you do what I say' and they would usually freak out, and take more if I asked. Not going to lie, this has happened to more girls than a number you would probably guess but I want to stress that I have never leaked or uploaded any of these girls' pictures.
Anyway this lasted from 2012-2016 and I have only stopped just recently, it was like some sort of sick addiction, like a twisted controlling thing it disgusts me now. To be honest, I am having trouble living with myself and don't know how I am going to enjoy life knowing that this will continue to haunt me.
I don't even know how to go about the legal aspects. If you were in my shoes, would you turn yourself in, I know that at least some of this is illegal (*mod edit*) but I basically just am depressed and can't forgive myself for what I have done.

This guilt prevents me from seeking employment, meeting new people, everything

If you think turning yourself in would a.) help with your guilt in the long term b.) ensure that you never repeat this behaviour, then it might be worthwhile - however, without contacting these women/ girls again it is impossible for you to know how they would feel about it being taken to court/ whether they would feel okay testifying etc.

I only know the law regarding this in Britain, which changed last year to illegalise some of what had not previously been illegal. Clearly some of this behaviour occurred when you were still a kid (15-17) but it sounds as though it has continued into your young adulthood.

The brain continues to change and develop until one's mid-20s so I definitely feel you can, to an extent, leave this behind you. The fact that you are reflecting upon what you did and feeling remorseful proves you can change and are not past the point of no return.

I don't know about the best way of making amends however. Obviously warning people about the potential dangers of online interaction would be a good start, as would teaching guys about enthusiastic consent and how wrong it is to blackmail people for nudes. Giving a monthly donation to a sexual assault prevention charity could be a good start.