Abusive and Blackmailing Ex

Hello,

I'm looking for advice on how to deal with an abusive and blackmailing ex-girlfriend who I have a child with. To give you a back story to get an understanding of my situation, will be slightly embarrassing for me, however I hope it will be understandable and I will receive some constructive feedback and some advice.

I'm a 40 year old male who is in full-time employment and have a very well paid job now. I have a girlfriend (GF4) who I've been with for 16 months and everything is going really well, we are looking at buying a house together and have the same goals in life.

When I was 18 I met a girl (GF1) and we got married, had children and purchase a house together. Throughout the marriage my wife was very possessive and jealous. I tried my best to settle her jealously by doing whatever she wanted. When I was 25 I decided to end the relationship because I had lost contact with my family and friends just to keep the peace with my wife. It was a very upsetting time for me because I was leaving my son at 5 years of age. At the time I lost my job and was in a lot of debt. The embarrassing thing for me and I am ashamed of it was that towards the end of the marriage I did start cheating on her, I guess because I couldn't see a way out and got comfort from someone else, this is something I should not have done. My son is now 19 years of age and I have paid child maintenance throughout and only stopped when he got a fulltime job.

The girl I was cheating with (GF2), eventually, we got together and was together for 10 years. During this time it was great, however there was a 14 year age gap between us (GF2 being older than me). At first I did not see a problem with this age gap, but over time it did become a problem as I was more out going and she was more stay at home and watch TV.  After ten years we had drifted apart and eventually we broke up. I would say this relationship breakdown was my own fault and not hers. I must state I was faithful throughout this relationship because I was ashamed of what I did with my first GF1.

After GF2 I lived on my own for a bit, eventually I started to like a girl and was trying to court her, eventually I found out that this girl was just using me for attention and I stopped chasing. This hurt quite a bit because she was leading me on and I think this is why I jumped straight into a relationship with GF3.

GF3 was a complete and utter mistake, most likely the biggest mistake of my entire life. Within 2 months she had already cheated on me (some may say pay back for what I did to GF1) but I stayed because I honestly don't know why (possibly scared of being alone). She was mentally abusive, controlling, gaslighting, you name it she does it. The relationship only lasted 16 months, however we had a child in that time. When my child was two months old she physically attacked me, this lead me to call the police, however she then decided to hit herself and accuse me of hitting her. This lead to the police dropping the investigation because there was not evidence and I had to go back and live with my mum and dad.

After breaking up with GF3 I started paying child maintenance through the CSA, and I have not missed a payment. Last year (2022) GF3 went out and got totally drunk and passed out on her bathroom floor whilst our son was asleep. I didn't know what to do so I spoke with social services about what I can and cannot do because I didn't live with her and I had to move back to my parents which live over 2 hours away. Because social services contacted GF3 she decided to block me from seeing my second son who at the time was just over 1 years old. I had to spent a lot of money in courts to get a court order to get access to my son which I have, it took about 6 months.

Recently, and this is the reason for advice, GF3 messaged me asking to pay half towards some shoes for my son, I declined because I am paying child maintenance (almost £700 per month). She got angry and basically said I'm not paying enough. Now she is basically blackmailing me saying that I need to pay more or she will look into getting more money from me because I'm still jointly mortgaged with GF1 who still lives in the property today. I've spoken with a solicitor and they've reassured me that she cannot get more money because I own a property (which is no rented out and I do not make any income from it).

But my main question is, how do I stop an abusive ex when I have a child with her and because the child is so young I have to go through her for contact?

Thank you for reading this and I understand I may get backlash from some of my previous bad decisions, which I am living with every day.