Two things may have happened. You simply didn't notice the looseness last week and as stated by the club members above, check out the suspension, however, 30K miles does not wear out lubricated joints. Aging of
struts, etc, could be a likely issue, my 2002 with 68K is still tight, a bit loose in
tie rods, but still very drivable as is.
Did you check tire pressure? To high will cause the car to be skitterish on the freeway, to low harder to steer. With 30K miles, thats the first thing I would check.
If it wants to wander a bit at high speeds that usually is not attibutable to things like
struts, but certainly
tie rods a bit loose, or maybe the steering rack, but again with 30K miles its probably something simple. If the wander is consistent in one direction, then its alignment time.