I am glad that you shared these experiences. Many people do not seek help for these problems until very late, ie until after a divorce happens.
Doctors call this vaginismus, or painful sex.
It can be a rather complex condition that might require a team to treat.
Firstly you could see a friendly GP who is willing to listen to your problems and have a check below. Otherwise, you could see your usual Gynaecologist (the one who delivered your previous children) to ask them for further advice.
Treatment will depend on the underlying cause and sometimes medications, surgery or psychotherapy might be needed. But first, we need to know the possible causes for it. Take care.