Not necessarily. It can take a while (up to a month) for your body to adjust to the medication. It's not uncommon for people to have a "fuzzy" or "underwater" feeling when beginning an SSRI like Lexapro.
To explain, Lexapro is an anti-depressant in the SSRI (Selective Serotonin Reuptake Inhibitor) class of drugs. It doesn't increase serotonin (a common misperception), it just makes the serotonin you already have more available for absorption by your brain. This process is going to have an effect on your cognition for a little while as your body acclimates to the effects. Once acclimated, you honestly won't notice any effect at all. However, it takes time. In general its recommended that patients stick with their meds for at least a month to see if they're effective.
That being said, if you have any serious side effects (a bad rash, etc) you should contact your doctor.
Additionally, I don't think that the Buspar would be slowing you down, but you might try decreasing it if it isn't needed (I'm assuming you take it as needed for anxiety).
I hope this helps!
When you say your thinking is "distorted" what do you mean exactly? Can you explain? If you're talking about a lack of concentration and a sense of dulling, then, yes - its normal and may subside over time. Again, I'd give it a month if it isn't getting in the way of daily activities.
If you're talking about thoughts that are bizarre or out of the norm, then no.
Yes, you should. If you don't start to perk up in 2 more weeks, then you should contact your doctor to discuss it.
I wish that I could say that we know these things immediately, but it really takes the body time to get used to the meds sometimes. In general you'll feel some of these weird effects for a couple of weeks and then the mood will start to improve, the anxiety will start to diminish and you won't notice any side effects.
I hope that's what happens in your case! I wish you luck!