Nausea and tiredness throughout pregnancy are affecting my worship. How should I manage it?

This religion is easy, and during pregnancy Allah lightens what is beyond your ability, so do not weigh yourself down with guilt. Allah does not burden a soul “beyond what it can bear” (Surah al-Baqarah 2:286). Perform the obligatory prayers as your condition allows, even sitting if standing is difficult. If severe nausea affects your health while fasting, there is a concession, and you can discuss it with your doctor and look up the ruling on making it up. Fill weak times with light worship such as dhikr, supplication and listening to the Qur'an. Intend your patience with this tiredness as an act of worship in itself. See du'a & prayer.