If its stress hypertension, then although a healthy diet will not hurt, it won't help to bring your BP down. Can you make a list of the practical things that are stressing you? I know that bereavement on its own is stressful as I lost my husband in 2011. There are various things that can help, talking therapies, support from friends or family or a bereavement group, meditation. Its about finding out what will help you. If the GP thinks that it is stress related, i wonder why he didn't tell you about what support is available locally...maybe you could go back and ask?