Did your therapist ask for your consent to share your children's details?
You realise that you have to consent to a safeguarding referral to social services unless your children are in immediate danger and in which case, it's not a safeguarding to social services its a call to police?
The therapist needs to give you all the information; what their concerns are, why they think it's a good idea to contact to contact social services rather than ie, the children's health visitor etc.
If they do not give you all the information then you cannot give consent because it's based on all the facts.
Many therapists state that if the conversations between you and them maybe private unless children are at risk etc, but they still must abide by safeguarding and GDPR.
It's the same with any professional. They need your informed consent to share your children's information outside of their organization.
So your therapist has taken advantage of their position when you disclosed. I would think about contacting your therapist and ask them where your children's details have been shared to and if this is outside of the organisation which is without your informed consent.
I would consider asking them why they didn't contact the police if they felt your children were in immediate danger. I would ask how much of your private sessions details has been disclosed as you said that you've offloaded a lot of your concerns to the therapist and the therapist may have policies in place that support them handing this over in the event of a serious concern.
I would also not wait for a social working team to ring me, I would take your children to their health visiting drop in and get their height and weight checked by a health professional so that someone in an authority position has checked your children over and can record their findings, telling the health visiting team what has happened.
You do not want to loose your children because you haven't been proactive. If the safeguarding has gone to social care (sometimes it's handled by the safeguarding officer of the therapy team who would contact you) then you need to work with them to ensure the safety and welfare of your children is paramount. This may mean you and your children living separately from your children's father.
Your children's father may now be under investigation and the social working team will need to contact you both to do a thorough check up. They may need to interview your children at school without you or your husband present to check whether your information corroborates with that of your children.