First, you've got two issues with causes that are almost certainly unrelated: thin negatives and pink base color. Fixing one of these problems will probably
not fix the other.
Concerning the thin negatives, it's impossible to say from your description whether your negatives really are thin; it's also possible that your commercially-processed negatives were overdeveloped and therefore too dense.
This Web page (and its
second part) describe how to determine the optimum film speed and development settings for you, your camera, your film, and your enlarger. (Note that film speed and development are interrelated.) Running tests like this is really the only way to be sure you're developing your film correctly. The development time charts you've probably consulted just contain suggested starting times; you might need to adjust your time up or down depending on your agitation style, thermometer calibration, and other factors.
Concerning your pink negatives, this is caused by dyes remaining in the film after processing. As others have suggested, this is often the result of inadequate fixing time; however, proper fixing time varies from one fixer to another. Rapid fixers usually don't require the 4-5 minutes that jovo suggests; they're usually in the 2-4 minute range. Consult the instructions on the fixer's bottle for details, or use the 2x clearing time rule (time how long it takes the fixer to clear a small strip of film and use double that time). Are you using a hypo clearing agent? If not, doing so may help speed up dye removal. So can extending the wash time. The dye itself is unlikely to be very harmful, as far as I know; however, conventional wisdom holds that leftover dye is often an indicator of inadequate fixing and/or washing.