When I was pregnant with my son symptoms would come and go all the time. One day my breast would be tender the next day they wouldn't be. Every day they weren't I would be so worried. Made me very nervous because I had a miscarriage a few months before at 7 weeks. The few symptoms I had faded the day or the day before I started having bleeding. I didn't have ms with either pregnancy. My next door neighbor is about 5 1/2 weeks pregnant right now and she had MS at 4 weeks then felt fine for a week and now it's back and worse. I wouldn't worry so much about the symptoms. It's pretty normal for them to come and go.
Different brands of pregnancy tests measure different amounts of hcg. Some brands can be positive with only 20 mIU/ml hCG and others need 50 to 100mIU. So one test may be lighter than another if it takes more hcg to show a positive. Also, if you are very newly pregnant it may depend on the time of day you are taking the test. First morning urine would possibly have more hcg in it then afternoon or evening.
I would recommend to take the same brand of test you have already taken tomorrow morning. Label all your test you have already taken with a date and time of day. That way you can more closely see the difference in the lines and compare. The test tomorrow should be darker than previous tests. It sounds like you would only be 4 to 5 weeks pregnant or maybe less because of your long cycles. It's not that unusual to get a faint line on 9-14 dpo. During my pregnancy I had a faint line at 11 dpo and a bfn the day before. (I only had 2 tests so I never tested again). I would possibly even call my doctor and request a blood test and tell them you are getting inconsistent test results over the last 3 or 4 days. They usually get the result back by the next day. If it were me I would call today so I wouldn't have to wait over the weekend to get the results.
It sounds like you had a miscarriage the time before. I'm sorry. It is pretty common to have a early miscarriage. If you do miscarry again I would definitely go and talk to your doctor. Sometimes there are medical reasons why some women cannot stay pregnant and lots of these issues can be resolved. I hope that's not the situation. So far it doesn't sound like it.
Stick bean stick!!!