I feel sick because I ate sushi yesterday if you use I think for this sentence its mean you have doubt about yourself

I feel sick. I think it's the sushi I ate yesterday. I ate sushi yesterday and now I feel sick.

"I think I feel sick because of the sushi I ate yesterday" or "I feel sick. I think it's because of I ate sushi yesterdayi" You can actually say "I think, I feel sick because of the Sushi ate yesterday." or say " I feel sick. I think it's because of the sushi I ate yesterday. "

Both are correct. 1.one: now I am feeling sick. because of the yesterday's sushi(I know the reason. but I am sick now) 2. one: now I am feeling sick. i have suspicions about the sushi yesterday.(I think it is the reason.), and here is the new one: 3. one. I felt sick because of the sushi yesterday. (I was sick because of the sushi. but now I am okay) so depend on what you meant you can use either.

In my opinion, the first one is correct. As for the second sentence, you can say " I feel sick. It's because I ate sushi yesterday " or "I feel sick. It's because of the sushi I ate yesterday. Can you see the difference between the two sentences?