Earlier quoted context omitted.
Just bear in mind that there's a huge difference between being able to get the gist of something spoken in a foreign language and being able to convey your thoughts effectively in that language. Even after man-years of study I still sound like an idiot when trying to speak English in conference calls, even though I can understand nearly 100% of written and spoken English.
Unless English is an easier language to understanding all broken up, nearly 100% of the time I can figure out what someone who claims to be "bad" at it is saying. English speakers, particularly in the US seem to be pretty tolerant of it. While other countries seem to be dismissive of anyone attempting their language, as if they can't POSSIBLY understand a single word you're saying. tldr: I'm sure you sound fine, and…
English has a massive variety of vowel sounds within its different accents, as well as other variations in length, emphasis, consonants etc. Native English speakers have a subtle ear for a massive range of vowel sounds (and plenty of people can reproduce them when speaking in an accent). A Spanish person can be confused if you substitute or mispronounce a single vowel in my experience.