Me and my ex husband switch years. Ive been getting the extra payments. Will i have to give that back or will they take that out of my taxes. The child has lived with me

If you do not claim the child as a dependent on the 2021 return then you will not be eligible for the CTC therefore you will need to pay some or all of the advance credit  back on the return which means you could owe.

Now this "switching" thing ... if you are the custodial parent you have the right to claim the child in full  UNLESS there is a court order to allow the non custodial parent to claim the dependency exemption (which includes the CTC) or you waive the right voluntarily by giving them a form 8332.   Read the rules here :

 There is a special rule in the case of divorced & separated (including never married) parents. When the non-custodial parent is claiming the child as a dependent/exemption/child tax credit; the custodial parent** is still allowed to claim the same child for Earned Income Credit, Head of Household filing status, and day care credit. This "splitting of the child" is not available to parents who lived together at any time during the last 6 months of the year; then only one of you can claim the child for any tax reasons. The tax benefits may not be split in any other manner. 

Note in particular that the non-custodial parent can never claim the Earned Income Credit, Head of Household filing status or the day care credit, based on that child, even when the custodial parent has released the exemption to him.

 So, it's good idea to let the other parent know that you will be claiming those items, as many first time divorced parents are not aware of this rule and may try to claim those items, which will cause the IRS to send out letters.

Ref: https://www.irs.gov/publications/p17#en_US_2017_publink1000170897

Scroll down to "Children of divorced or separated parents (or parents who live apart)"

** The IRS goes by physical custody, not legal custody, for who is the custodial parent.  Furthermore, for tax purposes, there is no such thing as joint custody, regardless of what your legal agreement says. The requirement, to be custodial parent, is that the child live with you MORE than 50% of the time. One of you has to be the custodial parent and the other the non-custodial parent. The IRS goes by physical custody, not legal custody. 

The $1400 round 3 stimulus payment and the child tax credit are two different things with different rules. If parent A received a stimulus payment for the child but parent B claims the child on their tax return, parent B will get a stimulus added to their tax return and parent A does not have to repay the stimulus.

However, the child tax credit works differently. If parent A receives advanced tax credit payments but parent B claims the child as a dependent, parent A will have to re-pay the full amount of the advanced payments and parent B will qualify for the full amount of the child tax credit to be added to their refund.

As discussed by the other expert, the rules on alternating claiming a child as a dependent must be followed carefully.  There is a potential for losing important tax benefits if the rules are not followed correctly. You should ask further if you have additional questions or need clarification.