At night I start to worry about things and then my chest tightens and I struggle to breathe. I think I have anxiety.

I am sorry to hear that you think you may be suffering with anxiety.

There are many symptoms common to anxiety and certainly those you describe could indicate this. 

If at all in doubt I would recommend you check with your GP or health care provider to get a correct diagnosis and alleviate any concerns you may have. They may also be able to offer further support.

You could also try AvenaCalm as this is traditionally used for anxiety and stress and possibly add in Relaxation Essence. Flower Essences help rebalance the emotions when we have emotional stress and can be taken when ever you feel you need something 'on the spot.' Just pop a couple of drops on the tongue. 

Do get your symptoms check if they are worrying you and I hope you are soon feeling better.