Privet. When we are counting the time that we have been doing something ("since birth"), we need to use the present perfect: "have" + past participle, in this case "been". Be careful with the article "a". Here is my short podcast explaining the difference between the different articles and when to use them: https://www.italki.com/en/podcast/episode/coh1dyg1vpvszcpnwaecgn?utm_source=copylink_share&utm_medium=share_content&utm_campaign=share_episode

Others have already corrected :), but if you like to talk more happy to chat, just send me a direct message through my profile :)