Hello...am I British?

Hello,
I have just started the process of trying to determine if I am a British citizen or not. I'm hoping someone might be able to help, or direct me to an organisation that can. The reason I am interested in this question is that I plan on relocating from the US to México within the next 6 months and would like to determine my British status.

I'm a 57 year old US citizen currently living in the US (Seattle, WA area). I was born in the UK (Swindon, Wilts) in 1957 and have a UK birth certificate. I also have a US DoD birth certificate issued from an American Military hospital in Wilts. My lovely mum was a wonderful English lady who married an American serviceman. I grew up being told by my parents that I have dual US and UK citizenship.

If anyone could point me in the right direction for info. I would be most grateful.

Thank you

I believe that you are. Apply for a British passport or confirmation of British nationality status.

Moreover, your children, if you have any, may also be British.

Thank you for your replies, they are very helpful. It looks like I may need a copy of my mothers birth cert., or passport. I'll get working on that.