I am so sorry. I normally avoid these threads as I'm scared of that very thing.
My MIL lost 2 babies in a row. One to SIDS at around 3 months & one at about 3 weeks, coz he was serverely disabled. About 4 years apart.
She told me it takes at least a year to even start to feel a bit better. Everyone is different though. Just remember to be strong for your other child. I know it must be hard. I can't even begin to imagine.