How long ago was this? The law was changed on January 2024 so that it's an offence to share simply without consent, whereas before it was necessary to prove an intent to cause distress. If you did this over 12 months ago, there's still a need to prove intent.
You can see exactly what counts as an intimate image by checking section 66D of the Sexual Offences Act. Without seeing the photo (do not post!) it's impossible to say.
Having investigated many of these cases (former police officer), before the change of law last year, they rarely resulted in prosecution. It's one of the reasons the law was changed.
As a domestic-related incident, the decision to charge this would rest with the CPS, not the police. Although the police would have to be of the view that there was enough evidence and public interest to make a successful prosecution a realistic prospect in order to refer it to the CPS in the first place.
If there's a documented history of domestic abuse with the OP as victim and the XP as perpetrator, this would probably fail that test and no action would be taken.
If you haven't reported the past abuse OP, that may not help you. It's one of the reasons I'd always encourage victims to report - get it on record so that a manipulative abuser can't use your silence against you.
Even if you went to court and were convicted, you'd never go to prison for this. You might even be offered a caution instead of court, or more likely words of advice if the officer investigating felt the case was significantly undermined by complicating factors such as previous abuse.
None of which alters the fact that this was wrong.