English To Spanish, Spanish To English

Hola todos,

I have mentioned several times by now how difficult the Spanish is here, and how difficult it can be to get around. This aside, I have been speaking a lot of Spanish and it is really improving. However, as strange as this seems, believe it or not, I feel like my English is getting rusty.  At least speaking wise. Since I have been speaking Spanish all day every day (except skyping with people from home), I know that the pronunciation, word order and words themselves are very different.
Here is an example of my English... what's the word I'm looking for?... Ah, deteriorating.
When I was in Mendoza on Saturday, we were looking for a place to have dinner and decided on a Tenedor Libre which is a buffet. The waiter asked what the translation was and I said, boofet ("t" sound included), I knew that didn't sound right so I corrected myself and said, boofay and again I knew that wasn't correct. Finally I decided upon the correct pronunciation being buffet (buhfay). I think the waiter was a little confused with my lack of my native language.
 Also, today I was in the library studying with a friend for a test that I have on Wednesday. Apparently her Spanish is deteriorating too because we both had trouble finding a word. We were looking for a word for when a business puts something into action. (The word was implement.) And we're saying, implentt? emplament? no, no! implemant? emplimant? Ah! What is the word?! She looked it up we both just sighed with a "Wow really??" look on out faces. It was a tragic experience and the English language is very upset looking down on me now.
I have also noticed that I am saying words and phrases in English that only make sense in Spanish. For example, the word "seriously" in Spanish is "en serio". Basically meaning "in seriousness." I am sad to say that I have said that a few times instead of "seriously." Also, I may have done this in my entries, but I have started saying, "for this reason" because "por eso" represents, "so, because of this etc., but more so, for this reason.)  For example: "I needed milk and for this reason I went to the store." This isn't grammatically incorrect, but who says that? One would say, I needed milk so I went to the store."
But on a better note, Spanish is also helping my English. Because my native language is English, I still do think in English when I am translating something or reading something in Spanish. I have realized that I use the word "so" a lot in English. So yeah. However, there is not really a word for "so" in Spanish. For that reason I have cut down on my "so" usage.
I am confused how my native language could possibly be deteriorating, and how a completely different language is ironically helping it as well. My English is going to be very weird when I return to the U.S.!!