I am not really knowledgeable but will try to help since your question doesn't seem to be getting answered. Allah is the most merciful, in prayer we may have distracting thoughts blocking us from fully commiting ourselves to prayer. One advice I could give is to truly feel like you are standing in front of Allah swt, imagine that this prayer is your last, fill your thoughts with piety. Fear his punishment, cry out to Him for repentance, with taqwa and imaan in your heart. But you are not sinful for something like this that is not in your control. If there is no reason to do ghusl, then focus on prayer and try pushing away any impure or distracting thoughts. Remember sister Allah swt understands your situation best, He created you, and He is your protector. But please do not think this is a reasoning for you not praying. Also if it is not too dificult, fasting is recommended for Muslims with this issue of arousal if there is no other halal option (marriage). May Allah grant you patience. Also if you are not sure if it is an orgasm while praying, then continue your prayer, if you find later on it was then redoing your prayer is the best option after becoming clean. May Allah give you strength to overcome your difficulties. Medication may help you with your hormones, I would advise you to see a trustable doctor if you can. Salalm