You must take him to the vet and also get a new temperature gauge today. Also give him fresh water daily and feed your gecko crickets and only occasionally give him meal worms.
Feeding Common House Geckos
House geckos should be fed a
variety of small prey items. Crickets can make up the main part of
their diet with the addition of fruit flies and other small flies,
silkworms, the occasional mealworm, and other insects. Gut load prey
prior to feeding them to your geckos, dust them with a calcium
supplement two to three times a week, and a dusting of a multivitamin
once a week. Feed your common house geckos in the evening since they
are nocturnal. Juveniles should be fed daily but adults can be fed
every other day. Feed as much prey as your house gecko will eagerly
Lighting and Humidity for Common House Geckos
Try to maintain a daytime temperature gradient of 75-90 degrees Fahrenheit with a night
time low of 65-75 degrees Fahrenheit. Heat can be provided by
utilizing ceramic heat elements or reptile bulbs in a reflector
lighting fixture. .../...
Use white reptile heat bulbs during day time hours. At night utilize a
red or purple night time bulb for heat. These bulbs can be purchased
in any reptile section of the pet store or online.
Common house geckos are nocturnal so they do not need special UVB
lighting like many reptiles. However, many experts feel providing UV
lighting is still beneficial to the overall health of nocturnal
animals therefore it is still recommended to use a UVA/UVB light bulb
during the day time.
House geckos need a moderate to high humidity level in their enclosure
so you should aim for 60-75 percent relative humidity which you can
measure with a hygrometer. Provide humidity with regular misting,
bowls of water, or a fogger and you will find that your geckos will
likely drink from water droplets left from the mist.
Put your own shame aside and fulfil your agreement to take care of him. He's alive it is not too late, but it will be if he dies.
If the temperature is out of range for him that could be making him ill, but seek the veterinary advice today.
We cannot control how others perceive us. If the vet is judgemental, there is nothing you can do about that. Most people understand a person going through difficulties, the problem is with a pet (just like with a child), they are dependent upon us and no matter what happens we need to put aside our difficulties to care for them. If we are failing to do this, it is our responsibility to seek help.
Now you are doing so here and good on you for that. Please go and get the help your lizard needs and let us know how you get on.