The last one, "I often go on business trips these days" is good. "I go on business trips often these days" is good also. The first one, "I have been going on business trips these days" would sound a little better if you said: "I have been going on a lot of business trips these days". My advice is especially good for conversational English. "a lot" means "many" and is often used for conversational and casual situations.

I’ve been going on business trips recently. I’ve gone on several business trips since March. Your other sentences are either wrong or unnatural. ‘these days’ talks about the recent past but as a contrast to something in the more distant past. For example, Early in my career I never used to travel. These days I do.