how many spots are there in the medical filed ?

That is a great question to answer when considering a job, but it is difficult to answer specifically. There will always be a need for physicians so there will always be job opportunities. It is important to consider the area of the country in which you want to practice. For example, some major cities like New York and LA have many doctors and it might be harder to find a job in those cities. The government provides funding for residency programs so there will always be training spots available, though some programs and medical schools are more competitive. It is important to consider your grades and test scores when applying to medical school and residency to ensure you are a competitive candidate. I recommend you do research in the area of the country you might want to work to get a good idea.

According to ONET, there were 30,000 Pediatricians nationwide in 2016. There are expected to be 1300 openings per year between 2016 and 2026.

https://www.onetonline.org/link/summary/29-1065.00#JobOpenings

Of these, 110 per year are expected to be in Texas. Texas had 2080 pediatricians in 2016 and is projected to have 2580 total pediatricians in 2026. These "openings" include both positions created both by growth in the industry and replacing doctors who leave the profession.