I used to have only a few students but in the last few days, I have gotten a lot more in a short amount of time, exactly 6 students in 3 days. I felt a little overwhelmed at first but gradually got used to it. I am a bit busier now so I am worried about the quality of my teaching. However, I will try my best to make sure I can handle all of them.

I used to have only a few students, but am these days far busier. Indeed, six have come to me in just three days. A little overwhelmed at first, I have gradually adjusted to the bustle. At the same time, worries over the quality of my teaching do trouble me a bit. Pushing those worries aside, I will do my best to handle my new increased workload. I have rewritten your sentences so that none but the first begins with "I", and "I" is used three times instead of six. As a matter of style, it is preferable not to start many sentences and clauses with "I". ALL of your sentences and clauses start, or almost start, with "I". Persistent use of "I" as a subject makes your writing appear to be self-centered. The suggestions I have made are intended to show you some ways to avoid creating this effect.

I used to have just a few students but recently, I have gained several more within a short time period — 6 students in 3 days to be precise. I felt a little overwhelmed at first, but I have gradually gotten used to it. However I am now busy worrying about the quality of my teaching. However, I will try my best to make sure I can cover them all.

I used to have only a few students but these days, I have been quickly gaining a lot more students: 6 students in 3 days to be more precise. I felt a little overwhelmed at first but but I gradually got used to it. Now I am just a bit busier worrying about the quality of my teaching. However, I will try my best to make sure I can provide for all my students.

I used to have only a few students, but recently, I’ve gained a lot more in a short period—exactly six students in just three days. At first, I felt a little overwhelmed, but I gradually got used to it. Still, I’m a bit busier now, as I’m concerned about maintaining the quality of my teaching. However, I’ll do my best to ensure I can meet all their needs.