If you're trying to get pregnant then yes having a thick yellowish in color vaginal discharge is a common early sign of pregnancy.
Most pregnant women will often secrete sticky, white, or pale-yellow in color mucus early on during the first trimester and throughout their pregnancy.
So if you're trying to get pregnant then the yellow mucus is a good sign and could mean that you're pregnant.
Even if you're not trying to get pregnant it's still normal for woman to sometimes experience yellow vaginal discharge and is usually nothing to be concerned about.