Can blood tests be false?

[Mel0519]

The last end day of my period was Oct. 3rd. My normal cycle is 5 days, a lot of cramps, heavy flow. It has been that way since I was 11 years old. I had sex with my boyfriend on Oct 14th. and on Oct. 23rd I was spotting with no cramps or back pain. It was on and off until the 26th. But it was barely enough to fill a tampon and it was really light pink in color and then a dark discharge at the end.
I'm 28 days cycle so my period should have been on Oct. 31st. So I indicated the spotting as implantation bleeding.
I took 5 pregnancy tests on Thursday morning Nov. 3rd it was positive faint but very visible. The rest of the 4 were negative. I went to the family doctor their urine test was negative and they made me feel like I was insane. Blood tests were done for diabetes and everything was perfect. I went to my gynecologist. I have a Pelvic ultrasound on Monday Nov. 14th. They did a blood pregnancy test and I cried yesterday that it came back negative. Because I have so many symptoms going on and no cause? We are thinking it might be cysts because I have been having abdominal pain/cramping. Can the blood test be wrong? Should I get another one done?

Symptoms:
Fatigue if I don't get 12 hours in I feel like I took a sleeping pill.
Lower back pain and cramping just like the feeling of PMS along with inner thigh/hip pain.
Mood swings if I'm not chewing someones head off I'm crying over anything
Breakouts pimples are like welts and they hurt so bad
I started getting very dizzy and nauseous on wed. Nov 9th. the feeling of a hangover that's all I can explain it as. It wont leave now. I feel like vomiting but I never can.
THIRSTY I cant get enough water.
The cravings for chocolate chip cookies, green beans, and yeasty bread. Its on my mind all the time and everything else grosses me out.
Frequent hunger pains
Bloating
Heartburn/Gass
Constipation
Headaches and nasal congestion daily.

They ruled out thyroid and all my levels look normal on the blood test and pap smear. So what can all this be coming from? I just want to feel better. :( But everyday I keep waking up feeling something is different or wrong and I'm not going crazy. If the blood test were wrong I would be about 5 weeks. Do you think that would be too early to tell for some women?
Please help me.

[Mel0519]

I looked at that information online as well. They just told me I was Negative. They never told me a number or any incite on different blood pregnancy test. I was thinking of bringing that up to them on Monday. I read that usually the qualitative blood test can be yes/no or positive/negative. So I guess I might need my arm poked 3rd time around. For the quantitative blood test.

[Clysta]

Often blood tests are not wrong, especially if you're having symptoms that are due to pregnancy. The only time they usually are is when they're done too early, but in this case that wouldn't apply. What blood tests did you have done? What many don't realize is that there are two different pregnancy blood tests. One is called a quantitative blood test and this measures the exact level of hCG in your blood--this test is never wrong. A qualitative blood test just looks for the hormone and gives you a yes/no answer. This one can be wrong. You need to have a quantitative blood test (also called a beta) done to find out the levels of hCG in your body--- if it is under 5, you know 100% you're not pregnant and you can start looking into other causes of your problems.