Should I put my son in therapy or is this normal?

I honestly can’t tell if this is normal for his age group or if he’s struggling. Also worth mentioning, my son is (I think anyways) slightly behind in communication skills. So “talking” isn’t necessarily helpful for him.

He’ll be 4 in 2 months. My dad passed away in November. My son noticed his absence pretty much immediately and started asking where he was. Then it turned into meltdowns about how he wants him back. At first I told him he was sick and couldn’t come back. But then someone made a good point and said that being detailed helps them more. So I explained that he had to go to heaven now and be an angel but that he would still be there with him as an angel, he just couldn’t see him. It worked for a little bit until he got sick last week. He started medicine and when I mentioned that to him, he said “i wanna give some to my papa so he can come home” 🥺🥺. I said “no honey, you can’t I’m sorry, your medicine is for you”. Now he’s back to talking about my dad all the time. I’ve tried to talk to him and just keep reminding him. I figured it was normal since he’s still young. But I notice that he seems to have a lot of separation anxiety too. Normally, he runs around and screams and plays. But now I feel like he spends a lot of time sitting on my lap or trying to physically cling onto me and tells me “I want my mama back”. The “I want you back” part worries me because that’s what he said about my dad, so I’m worried he thinks I’m next or something. Now he also keeps asking me to sleep with him in his bed. Last night, at 3 in the morning, he woke up screaming and crying for me. I opened his door and it seemed like he was doing it while he was sleeping. So I’m guessing he had a nightmare 😭