Does my cactus have an infection?

Try squishing a few of these white dots and see if you get a red juice. If you do you have cottony cactus scale on the cactus. It would help to see a picture of the problem.

hi im mike the best thing for it is get sum soil mix from walmart for catus if not able to get some sand like play sand from somewhere and sum potting soil and sum little pebbles like fish tank rocks and mix it all together so its sandy soil make sure its as dry as possable i say this cause u r either watering it to muc or it isnt draining rite and the mostness is doing that to ur plant ok atleast the white part and the bubbly part the dots may just be part of its natural growing ok back to the soil after u mix it all up get a small towel wrap it slowly and gentaly so u dont crush the needles of ur catus but so it doesnt stab u and have a butter knife with u and tip the pot over on its side make sure to have sumthing for the dirt to fall in ok scrape the dirt out of the pot b carful around the plant after it comes free from the dirt rinse the roots in low stream water luke warm and rub it softly gettin any rotten stuff off if any is there then put it down on its side while still in the towel ok now clean the pot out of all dirt and wash it with dish soap rinse and dry then put the soil mix from above half way full in the pot then put the catus back in it fill the rest of the pot dont packed it down let it stay lose ok now take the towel off slowly now that it has been repotted and sitting in the middle of the pot not falling over take a Q-tip and lightly brush the dry white stuff off the places u have seen it try not to blow on it the needles my fly off onto u or the floor ect u dont want any to get u lol finally in a week put a small amount of water in it and water it by weekly with small amounts u could go as long a month without watering it after the first time i hope this helped if u need more help let me know