considering

I have been divorced for a year now, my ex and I were ttc for 2 years and found out he could not have kids (not the reason we broke up) but now that I am single I have been considering finding a sperm donor and doing it myself since I have wanted kids for so long now. My mom has stage 4 metastatic breast cancer and it's gotten bad. I would ideally like to have kids before she dies and yes I know there is a possibility she could pass before or during my pregnacy even but it's really important to me. Here's the issue though, I don't know where to start and I don't know how to explain to my boyfriend what I want. We are not serious and not sure how he will react...