In reason of their common Latin ancestry, a lot of English and Spanish are very similar. In most cases, the meaning is the same or very close, but sometimes, there are large discrepancies.
For example, if you’re trying to say I am embarrassed, be careful not to say Estoy embarazada, because you are actually saying I am pregnant, which is actually even more embarrassing! Rather, you should say Me avergüenza.
Similarly, if you are constipated, don’t tell the doctor that you are constipado, as that would mean you have a cold!
There are many other interesting false friends between these languages. For example, this article has a list of 50.