How to overcome my sisters taunts over my baby rejecting me?

I had a lot of trauma built inside me prior dating a narcissist and after we broke up- it shattered me. He hurt me soo much and destroyed my will power for life and everything I had inside of me. So fast forward I got married to someone else ( rebound) had a baby with him, but I started lacking empathy for this world. Later my husband didn't show me affection or love but I gave birth to my child via c section. Anyway after my operation i couldn't walk or move for 2months, and my mum was helping with baby as I was staying at mines instead of my baby dad. So my son became attached to my mother ( his grandma), however as a mum now myself I gave my son time during my degree/operation, but then later for a month had no time to give him as I had deadlines so everytime I'd be around him I got abit distracted but had to complete my final year and did. The issue is he likes my mum over me and wants her more than me and cries for her sometimes but my older ĺsister always makes comments by laughing at how my son rejects me. We both planned to do a joint birthday party with both our kids but she goes she wanted to chuck "a who will the baby go to competition" and then she recorded my son going to a cousin of mines today rejecting me when we held our hands out on to who he will come too, and making comments how her child goes to her and mines doesn't. I felt soo rejected and embaressed that I felt like I wanted to kill myself over the fact I birthed my child and the rejection hurt so bad as I got rejected everywhere growing up, and for my sister it was a laugh, but I locked myself up today in the room in agony of the hurtful comments my sister keeps making over my child. After i got my degree i give him time, even look after him and look out for him and made sacarficies to priorities him but I felt crushed today at the fact my cousin wanted that video but I didn't want my sister to send it to her. Then my sister said if I deleted that video on her phone that means am insecure.

How to overcome my sisters taunts over my baby rejecting me?
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