[Al-Baqarah 184] [Fasting for] a limited number of days. So whoever among you is ill or on a journey [during them] - then an equal number of days [are to be made up]. And upon those who are able [to fast, but with hardship] - a ransom [as substitute] of feeding a poor person [each day]. And whoever volunteers excess - it is better for him. But to fast is best for you, if you only knew.
If your problems stem from a temporary illness, then all you need to do is make up your fasts at a later date when you are able to do so. According to the Hanafi school, these days need not be made up immediately. It is, however, recommended to do so, and dying while these fasts are not made up (without a valid excuse) is considered sinful.
If, however, your problems stem from a chronic condition (e.g. diabetes) wherein you are unable to fast without severely impacting your own health, an alternative is provided: Feed a poor person for each day you miss, after which you no longer need to fast for those days.
The symptoms expressed may be a result of illness (chronic or acute) or possibly just due to poor eating habits during the month. Diagnosing such things is (obviously) out of scope of this site, but given that many people can fast the month regularly without such problems it is probably worth seeing a doctor about it.