I'm having early symptoms of pregnancy but i'm also on nexplanon which has similar side effects also i have irregular cycles when should i take a test?

Pregnancy symptoms: Go ahead and take a home pregnancy test now. It is common to have irregular spotting when you're on Nexplanon. It is a very good form of contraception, but none of them is 100%, so it's best to check. If/when the test is negative, then you'll know that the symptoms you have are just from the spotting. They may go away the longer you have the Nexplanon in place.

3 weeks after sex: A urine pregnancy test, done correctly, gives a reliable result 3 weeks after sex (3 weeks after when conception might have occurred), or 1 week after missing a period. If done sooner, a positive result is likely real, but a negative result may be due to testing too soon, and thus lead to a repeat test. If a woman gets her normal regular period, then she is not pregnant, and a test is not needed.