I was going to Tokyo for a job in this weekend.

But two days ago, iI went to see a doctor twhenre I got a positive result foron a pregnancy test!

Just a few small suggestions to make your sentence more natural. To rephrase it further, I'd say:

"But two days I ago, I went to see a doctor for a pregnancy test, which was positive!

But honestly I'm concerned about continuingthe pregnancy because I was undergoing fertility treatments and finally got pregnant.

"I'm concerned about continuing the pregnancy" implies that you are thinking of terminating the pregnancy. It sounds to me like you're trying to say that you're concerned about the pregnancy. This implies that you're concerned for the well-being of your new baby.

Don't worry - those concerns are normal!

I was going to go to Tokyo for a job in this weekend.

But two days ago, iI went to see a doctor thenand I got a positive result for pregnancy!

But honestly I’m concerned about continuingthe pregnancy because I was undergoing fertility treatments and finally got pregnant.

This wWeekend

Title capitalization rules

I was going to go to Tokyo for a job in this weekend.,

I was going to Tokyo = you went to Tokyo and you are about to elaborate further
I was going to go to Tokyo = you had plans to go to Tokyo, but ultimately, you did not go

This sentence is better joined with the next line

Bbut two days ago, iI went to see athe doctor then Iand got a positive result for pregnancy test!

I’m spending a really cozy time at home.

But honestly, I'm concerned about (continuing) the pregnancy because I was undergoing fertility treatments andbefore finally gotetting pregnant.

Concerned about continuing the pregnancy = you are considering getting an abortion.
If you just mean that you are a little bit worried if the pregnancy is going well, just remove "continuing."

I’m going to see a doctor next week.

Alternative: I’m going to the doctor next week.