When the contraceptive pill is taken correctly its effective in preventing pregnancy.. but there is still a small chance of pregnancy even if ejaculation doesn't occur inside the vagina. Take a test to confirm

It could be because of many reasons like stress, thyroid, hormonal imbalance. Talk to gynecologist for thorough evaluation

Not getting your pe­riod on time is concerning, but we'll find the­ cause. You mentioned ge­tting intimate in late March, which could be the­ reason. Sometimes, this shifts your cycle­. Other possible causes are­ stress or certain medicine­s. If you feel queasy or tire­d, doing a pregnancy test at home may he­lp.

If your last period was on March 26 and you suspect pregnancy from early May, pregnancy tests might not show accurate results if taken too early. Wait at least a week after a missed period for a more reliable test. Use your first morning urine for better accuracy. 

CONTINUE taking 50 mcg of thyroid medication during pregnancy as TSH levels may fluctuate during pregnancy!! Lowering medication may harm the baby. Consult with your DOCTOR before making any changes.

While it's less likely to conceive right after having your period, it's still possible to become pregnant at any point in your menstrual cycle, including during the days immediately after your period. 
If you've had unprotected intercourse and missed a period, it's important to consider the possibility of pregnancy and take a pregnancy test to confirm.