OP I am so very sorry this has happened. How utterly terrifying it must have been. A real line has been crossed, and you've sensed that which, in a horrible way, is good, in that it gives you the impetus to get help.
You've had some good information and advice above. PLEASE get to the police today. That will give you access, I hope, to the safety, justice, and clinical care you and your DC need.
The law changed last year to make non-fatal strangulation a specific offence, with a 5 year sentence, for good reason. Legal, medical and policing fields are finally acknowledging the severity of this most terrifying of acts. As PPs said, after a woman has been strangled, she is over 7 times more likely to be a victim of homicide. People above have mentioned the danger to structures in the neck. Perhaps what's new, and what led to the law changing, was understanding the impact on the brain. Pressure on the neck can prevent blood entering and leaving the brain, which can lead, in a matter of seconds, to brain damage. Some of the areas most vulnerable to hypoxia (reduced oxygen) include the parts of the brain responsible for problem-solving, decision-making, judgement...so, as well as the fear and shock you must be experiencing now, I can imagine it might also be difficult to think your way out of the problem. Another reason why it would be good to listen to all the advice above. Let the wisdom of MN do the thinking for you!
There is also the risk, due to damage to the arteries in the neck, of clots forming and delayed stroke. This can be delayed by weeks, even months. There is good evidence that strangulation might actually be the second most common cause of stroke in young women. Horrifying.
And that's why you need to get help now. I hope the police will send you for medical examination. This is so important. I would also strongly suggest contacting Women's Aid.
Below is a link to a really helpful information leaflet for women who have been strangled.
I wish you strength. My heart goes out to you. Keep yourself, and your DC, safe.
https://static1.squarespace.com/static/63bd7ef0794e9f154bdce4ce/t/64131368ee0266496d81dde8/1678971753356/IFAS+01+-+Patient+Information+v5.pdf