When should one take a pregnancy test if she has irregular periods?

If she track her intercourse dates, she can test around 10-14 days after the intercourse. Sometimes one will experience pregnancy symptoms like nausea, hungry, tired, sleepy, bloated, and etc and you can ask her to take pregnancy test if she has these symptoms. I did not have mense due to breastfeeding and did not plan for pregnancy no.3. I realised I might be pregnant as I feel hungry all the times (I am a small eater normally). So I get a clearblue digital test and it said I am 2-3 weeks pregnant.