Is it ok to go for a trip while 28 weeks pregnant?


I booked a trip long ago to beautiful Hawaii this coming January which takes 6hours flying, I will be 28 weeks pregnant with my first baby boy. My doctor said that my pregnancy is healthy and I can travel with no problem, but my cousin just got me very worried saying that I shouldn’t do that coz air pressure, altitud and so many not very good things. Now I don’t know if cancelling or not. What do you think? Please some advice from mommas who traveled or if you know someone who traveled at that stage of pregnancy? Was everything fine?