Welcome to our forum and sorry to hear you are feeling well.
It is important to take your Levothyroxine pill on an empty stomach with a glass of water, 1 hour before food, 2 hours before supplements and 4 hours before calcium, iron or vit D supplements.
I don't medicate amitriptyline but have read it must be used with caution in people with hypo//hyperthyroidism but do not know why. If this were me I would seek further clarification that these meds can be taken together.
Levothyroxine takes up to 6 weeks to initially saturate the body which will only tolerate small increases at any one time and your doctor should retest your thyroid hormone levels after 6 weeks and adjust the dose according to results.
Leave 24 hours between last dose and blood draw and try to have the blood draw early in the morning when TSH is highest.
Anxiety and depression are classic low thyroid symptoms and you may find improvements once you are optimally medicated. These symptoms are also classic of adrenal problems so eating well and looking after yourself will help. I supplement Vitamin C to aid adrenal health but there are many other helpful supplements.
Ask your GP to test Vit B12, folate, ferritin, Vit D as these are commonly deficient in people with low thyroid hormone and optimal levels are required for good thyroid hormone synthesis. Low levels could also account indirectly for anxiety and depression.
Supplements Known To Aid Thyroid Function