I too have TNBC. Diagnosed March 2012. There are a few of us in TN group of you would like to access the conversations, although I think they are all open for general reading. I can't help with the panic attacks specifically except to say that I think we all have them. Whether during treatment or in the middle of the night when we are insomniacs. For myself, I experience anxiousness and a bit of panic every treatment partially due to some complications I've experienced and partially due to the knowledge of what the treatment will bring - I dislike being sick and dependant. I now also understand that the steroids have an effect on my emotions and mental state - something I didnt realise until after my first round of chemo. I use relaxation and meditation to work through these periods. If your doctor had given you medicaiton that assists you accept it. The whole BC diagnosis and treatment is very difficult and I found I had to accept help in many forms to successfully navigate treatment. If you are concerned re addiction then address this with your doctor as well.
As for food and cravings - go with what is good. First round of chemo I craved salty little things. Now I have no taste buds from day 3 to about 8. And when they come back nothing tastes the same. Jelly snakes are good though on day 9. I would kill for a good cup of tea and marmalade on toast that tastes like it should, or how I remember. If cake is your current favourite, eat it. When possible ensure you are also having fibre and water (chemo effects you if you dont). If you have concerns re your diet speak with your medical team they are there to support you, to enable you to get through the treatment with as minimum stress as possible. No question is a silly question.
Most of all be gentle on yourself. Take care and onwards we all go.