Pearlscaled Goldfish

Question
I have a little pearlscale named Mabel that lives in a baby bio orb that holds about 3.5 gallons.  Her water is at room temperature and I turn the light on to warm it a bit everyday at least twice a day for a half an hour or so. I clean the tank about every four weeks when a filter change is needed and change out some of the water once a week.
Oh and I feed her flakes, which I know can cause swim bladder problems, and it's something I've tried to fix, but she won't eat other things. I do feed her shelled peas regularly to try to avoid swim bladder problems, but in the past three months she's been getting sick more often. Sometimes it's her swim bladder and sometimes it's very mild. Sometimes it's red streaks on her fins and redness at her gills. For a while we thought it was from the tap water - when I was at college she lived in all store bought water as I knew that water would kill her. She's continued to get red streaks when ammonia shouldn't be the problem, however.
I've changed back to all bought water.

So here's what's up. She's been very inactive for the past couple days, usually sitting on one of the leaves of one of her silk plants. I put her in a large, one gallon vase last night to feed her a pea, because I thought she seemed to weak to chase it down in her filtered tank. I've done this in the past and she gobbled it down.
I last cleaned her tank two or three weeks ago and because i had no water for her at the time, i put the new filter in without changing anything out and then cleaned the tank as usual the next day. Last night i decided the tank looked cloudy and it was probably due to the new filter being tossed into a dirty tank. SO I changed everything last night.
Last night she spent much of it resting near the bottom, fighting to maintain her upright position. Occasionally her breathing would appear to stop for about ten seconds. I thought she'd be dead in the morning, but she's still going, albeit weakly. She has trouble swimming higher than an inch or so off the bottom and sometimes her movement is very rapid in what I assume to be her struggle to rise.
Sometimes she is resting at the bottom and rotates upside down, probably from the swim bladder. She swims very little and is not eating.
You said you needed detail and this is about everything I can think of. At this point, I don't really expect to save her, but if you had some miracle advise, I'd certainly take it.
If not, how long should I let her go on like this? Is there anything I can do to help her? Is there a way to humanely end her struggle?
I love this little fish and I'm completely at a loss of what I can do for her. I've done everything I know how.

Thank you for any advice you can offer.

Answer
At the risk of sounding rude, your tank is way too horribly small, and you should be doing water changes two or three times a week - NOT once a month. Once you get your goldfish a larger tank and pick up on your cleaning routine, you will see a huge improvement. At the rate you're going right now, your fish will not make it. PLEASE study up on goldfish care by a commendable source.
Thanks.