What are the signs of Autism?

I just need advice. So my son is about to turn three next month, and he doesn’t say a single word. We do speak two languages, and I sometimes think that might be a factor. He is currently in speech therapy, and he has improved in some areas but no words yet. His therapist mentioned that he is raising some red flags for autism. I don’t think that’s the case; he is a very smart boy but now that she brought it to my attention. I don’t know if I’m just in denial or what. It hurts me; I sometimes feel like a failure. A lot of people I know tell me not to worry about it, that boys take longer to talk and that they know little boys who didn’t talk until 3. My son doesn’t interact with kids, especially right now during COVID. We take him out to parks on our days off. I guess I just need some advice from mommas going through something similar or who have gone through something like this. Thanks a lot!