Can my ex-husband force me to sell our house if both our names are on the deeds and mortgage, our 18 year old son still lives with me. Our son doesn't want to live with his dad and his dad hasn't got room for him.

You say your husband is "ex," but have you actually gone through divorce proceedings? The ownership of the house should have been settled at that time. But to answer the question: no, in case of joint ownership one party can't force the sale of property. However, he can make it very difficult for you to keep it - he can stop making payments on the mortgage and real estate taxes, forcing you to cover the full amount yourself or risk losing the home in default.

Back to the issue of the divorce - if you haven't started proceedings you should contact a divorce lawyer immediately. It's the best way to protect yourself, especially in cases like this.

There is too little info here to properly answer. As noted, you didn't indicate whether a divorce order/settlement has been made by a court as yet. Any question on law needs to include your general locale as laws vary by area.

For example, it is possible, depending on the terms of the divorce, that he can force you to buy him out or sell the house. Its also possible he can sue for partition of the house and force a sale.

As for your son, he is 18 and can choose where to live.