Still grieving my mother in law's death even though we didn't get on (TW death/grief)

My mother in law passed away suddenly at the beginning of November last year and I don't think I know how to handle it very well.

I'm only 22 and haven't really experienced grief like this before. I look at my partner sleeping at night and I feel like bursting into tears that he only had his mum for 22 years. Our son is 2 and the thought of only 20 more years of cuddling breaks me into pieces.

His mum and I didn't get on very well. I was his first girlfriend and he stopped helping his family as much when I came along just because he started being a teenager living his life. He never stopped loving his family but she acted like he couldn't have both. After we moved away, she stopped making an effort and didn't visit until we had our son and even then he was 8 months at that point. We never argued but things were tense and I think we always knew there was a mix of tension and respect for each other.

In her final months, she was actually quite kind to me it was like she was finally seceding and accepting that I had been positive for her son. She started making an effort to let me know she thought I was doing a great job with my son.

The night before her stroke, Sunday, I nagged my boyfriend to call her. I can't remember why I just felt like he had to call her to tell her something or show her our son. By Tuesday, I stood in her hospital room trying to look anywhere but at her laid on the bed gone.

Since that day I've thought about her every single day. I feel guilty for being this upset when we weren't close. I don't know how to feel about anything. I talk to my son about her regularly because he finds it comforting. My partner doesn't want to talk about her and truthfully i don't know how to talk to him about this we were going through a hard time before she passed and now i feel like i am juggling supporting him through his grief and working through past issues and mistakes. its just so overwhelming. How can someone just die so suddenly with nothing left behind not even a heartfelt text message for my partner to remember her by.

I just needed to vent really. I might write a letter to my son. everything thats happened has just shown me how painful it is to not have words of love to comfort you. I don't want my son to wonder how much i love him ever even if he moves away one day.