Regardless of whether you feel the skin damage, it's still there if you're going back to back like that. Every now and then is one thing (like when you're on vacation), but doing this on a regular basis can break down the elastin in your skin (due to not giving your skin enough time to replace vital nurtients that are lost during the tanning session) and will lead to wrinkles a few years down the road. Anything over moderation raises the risks of major damage.
It also helps to understand how tanning works. During a tanning session, your skin is hit by UVA and UVB. UVB causes melanin production, and UVA changes the color of melanin once it hits the surface. It takes anywhere from 24-48 (some experts say even longer) for new melanin to reach the surface of the skin, where it is tanned. Tanning before melanin reaches the surface does little to no good, but does cause your skin to dry out and lose nutrients. So, in short, tanning every other day is just as effective for color change (if not more) and less stressful on your skin. Skin damage is permanent...you don't get a second chance. Why risk it?
As for your question....are you using a bronzer? (Most SB products have bronzers in them) If so, it may be the bronzer that makes you look
bronze instead of brown. Especially if outdoor tanning makes you brown.
I would try a good accelerator or tingle lotion without bronzers for a while and see if that helps.