I know you are using a big dose of Oestrogel (4 pumps?) so I think there is something else going on if you are still getting flushes and shivers. I am using 2 pumps per day and it's working really well - I apply it every morning to inner thighs. Have you had your thyroid checked?
A colleague at work has to use HRT plus Citalopram alongside to relieve her flushes.
DG x