5 days into 10mg

I just started 10mg amitriptyline about 5 days ago for abdominal pain that might be related to ibs and the first two days I had the normal side effects like next day drowsiness and it seemed like it might be helping with my anxiety. But for the last two I’ve had trouble falling asleep, minor heart palpitations after waking up, and an increase in anxiety and irritability. Did anyone else have these initial responses to the meds and then get better? I’m wondering if this is temporary and I just need to get used to it or if it means I need to stop taking it? Should I cut the pill in half and take 5mg? I just don’t know what to do. Thank you in advance to anyone who takes the time to read and reply, it would mean a lot.