brown spots on face

Only until recently (2yrs ago) my skin on my face goes brown in areas after sun exposure but fades away after a few weeks. i've never had this before and now it puts me off going away on holiday as it ends up making my face look dirty. Im 30 years of age and don't want this at such a young age. Can you recommend a face cream i can buy from boots and can use daily to avoid this happening again. Im worried that they will appear each and every time I'm exposed to the sun now. i've never had them before and they've only appeared in my late twentys. It's embarrassing for me and i'm in desperate need for a treatment thats affordable.

Thank you

Sarah Miller