So I had sex 3days ago before that 10days my period is now 2days late just took a pregnancy test and it's negative and my breast are sore... Did I test too early? How long should I wait to test again ?

About 2 weeks past your missed period.

First normally unless you are on birth control that regulates day of period, 2 days is not even considered late, most women are a day or two early or a day or two late, all the time.

But yes of course having sex you can be pregnant,

Most tests are not reliable at 2 days late, and will give false negative readings all the time.

You need to be at least 14 days late to start testing, then use the first urine of the morning, as soon as you wake up

If you had sex 3 days ago you wouldn't even be pregnant yet. Do you know how reproduction works? You definitely tested too soon.

Two days late is nothing, and isn't even considered late when testing for pregnancy.

You need to wait until your period is at least 2 weeks late, then test with first morning urine. If that test is negative, wait for your next period, and if you miss it, test again or get a blood test.