I don’t know if I should tell my ex I’m pregnant

I think first you should confirm you are actually pregnant, this makes is easier instead of relying on if's. Then I think you should tell your ex, whether or not you keep the baby is up to you but he still deserves to know. Lastly with your friend, If your friendship is true and she is truly over what happened she should support you with either decision you make. If she doesn't want to be friends then that's her loss okay. I really hope this helps but ofc I would also recommend talking to someone else you trust for another perspective. You got this

Sleeping together yet presumptions of being pregnant did you guys have unprotected in order to think your pregnant?

If you are absolutely dead set on termination, then I don't see much point in telling him, what would he honestly do with that information since he has no influence over it? It does seem a bit silly for your mum to say it's nothing to do with him though and is possibly letting her own feelings cloud her advice,

Honestly your point is why I’ve been so torn about it because I wouldn’t want to spring that information on him when he can’t do anything to help or support me but on the other hand a part of me thinks he has a right to know and I wouldn’t want the information to ever get back to him through someone else. I think my mum has a good point but also might be saying it because she thinks it will do more harm than good

I think the way I'd look at it is what positives could come from telling him? I'm struggling to think of 1
If you were still together or even wanted to be I'd say it would be different, likewise if you were planning to raise the child - I'd say that was closer to 'right to know' territory. But if you're not going ahead, that's your choice that he would never be due a say in and renders almost all reasons to tell him moot.
I wouldn't share this with your friend, as the chances of him finding out are pretty high since they have shared history. I suspect your mum is laying it on a bit thick and she worries if you involve him that's it, he's back in your life again, she possibly for whatever reason just wants him out of the picture.

Thinking about this as a guy - I personally would not want to be told such a thing 'I was pregnant with our child but decided to terminate', as there is nothing constructive I can do with the information, it's just a big unresolvable ??? in my head wondering if it was done out of spite or even a lie.

if ur gonna have an abortion then there's no point in telling him but if ur hoping that he'll get back with u and have the baby together then tell him

Hello,
I dated this guy 4 years ago and he was my first official boyfriend. I found out after we broke up that he was cheating on me with this girl he casually dated before I met him. I met the girl a few months after and we have been best friends ever since (she didn’t know about me either). I am now In a close friendship group with her and 2 other girls I met through her. A few weeks ago I saw my ex on a night out and we ended up sleeping together without protection and now I have missed my period. I told my friend that I slept with him and she found it weird but got over it. I told my ex that I didn’t want to lose my friendship with her so we couldn’t speak to each other or see each other ever again. I’m terrified that if I am pregnant that she won’t want to be friends with me anymore and I don’t know if telling him is the right decision. In my head it’s the morally right thing to do but everyone has told me it would be a bad decision (If I am I will be getting an abortion regardless).
Any advice would be greatly appreciated x

Thank you for the advice it has really helped x

Hello,
I dated this guy 4 years ago and he was my first official boyfriend. I found out after we broke up that he was cheating on me with this girl he casually dated before I met him. I met the girl a few months after and we have been best friends ever since (she didn’t know about me either). I am now In a close friendship group with her and 2 other girls I met through her. A few weeks ago I saw my ex on a night out and we ended up sleeping together without protection and now I have missed my period. I told my friend that I slept with him and she found it weird but got over it. I told my ex that I didn’t want to lose my friendship with her so we couldn’t speak to each other or see each other ever again. I’m terrified that if I am pregnant that she won’t want to be friends with me anymore and I don’t know if telling him is the right decision. In my head it’s the morally right thing to do but everyone has told me it would be a bad decision (If I am I will be getting an abortion regardless).
Any advice would be greatly appreciated x