If you are a trans man it is possible to get pregnant if you have frontal sex without a condom.
Testosterone is not considered birth control and it is still possible to become pregnant whilst on Hormone Replacement Treatment (HRT).
If you are on HRT, more suitable contraception methods may be non-hormone or progesterone only based birth control such as the copper coil (IUD), the progesterone pill, the Depo-Provera injection or the arm implant.
If you are not on testosterone HRT, it would be advisable to explore all forms of birth control.
For full details of contraception choices available to you visit Sexualwellbeing.ie