I have diarrhea.
我在拉肚子。

Diarrhea [ˌdaɪəˈriə]
拉肚子，腹泻

Diarrhea is where you have to poop often,
腹泻是你经常要上厕所，

but when you do it is very watery, and you usually have an upset stomach, too.
但排便很稀，很多时候还伴随肠胃不适。

Diarrhea can cause serious health problems if you have it for a long time.
如果长时间腹泻，会造成很严重的健康问题。

What other symptoms are you experiencing?
还有其他症状吗？

Symptom [ˈsɪmtəm, ˈsɪmp-]
症状

A symptom is something unpleasant that points to a larger problem.
症状是指一些可能导致更严重问题的不适。

For diarrhea, some symptoms of this issue are having an upset stomach and having to rush to the bathroom a lot.
对于腹泻来说，其中一些症状是肠胃不适和得经常冲去厕所。

If you have the flu, you can tell the doctor: "My symptoms are a high fever, sneezing, and body aches."
如果你得了流感，你可以和医生说“我的症状是发高烧，打喷嚏还有身体酸痛”。

Experience [ɪkˈspɪriəns]
经历 v.

To experience something means that you have to go through and deal with it.
经历某事是说你得承受并解决某事。

If you are experiencing symptoms of diarrhea, this means that you are probably suffering through an upset stomach and having to use the bathroom a lot.
如果你在经历腹泻的症状，意思是你可能遭受肠胃不适和频繁上厕所的折磨。

You can experience other things, too, though, and they don't always have to be bad.
你同样可以经历其他事情，不一定是不好的事情。

If you got tickets to see your favorite singer and someone asks you how the show was, you can always say "It was a wonderful experience."
如果你买到了票去看你最喜欢的歌手，有人问起你表演怎么样，你就可以回答“真是段美好的经历”。