If it makes you feel better, LSD is a lot 'stronger' than LSA. There are very few chemicals that are more potent than LSD - off the top of my head, the only one that comes to mind is ALD-52 (LSD that has been further modified). Of course, that doesn't really matter, because (in order to trip) you simply do more LSA to compensate. But you needn't worry that you took some mega potent chemical that will rot your brain - you'll be ok!
As for the dose you took, it was a low one. If you just ate the seeds whole, I wouldn't be surprised if you never even got high. In the future, I don't recommend consuming those seeds. I don't know if anyone knows all of the active chemicals in them, but they do cause nausea and cramping (though you could say the same about some other hallucinogens).
Regarding your symptoms, it is almost certainly anxiety related. You were normal after you did them, and only later did you think you might have flashbacks.
I think it might be helpful to explain a little about flashbacks. The perception you may have received from movies, television, and classroom anti-drug programs is very likely to be exaggerated.
First, flashbacks are not as common as you might think. Most users of LSD (you know, the real stuff) do not experience flashbacks. Of those who do, the vast majority do not 'flash back' under normal circumstances. Some of the most common situations which cause a flashback are drug use (hallucinogens or marijuana), intention (some people can concentrate and essentially will themselves to have a flashback), and extreme stress/fatigue. It isn't as if you wake up on a Sunday morning and you're in outer space, but if you have done hallucinogens on several occasions, and at some point in the future stay up all night long on loads of caffeine and smoke a joint... that may well cause a flashback.
What is perhaps more comforting is that a flashback is not actually a 'flashback.' Generally speaking, a flashback is the feeling of LSD-like effects - you are flashing back to that tripping state. However, they're typically mild, and only brought out on rare occasion (and even then, not for all users). The frequency with which you flash back depends mostly on your brain, your environment, and how many times you tripped - it's not very predictable. I suppose that if someone tripped an incredible number of times, it could cause permanent or semi permanent problems.
As for what the flashback is actually like? Imagine a few points of light in the periphery of your vision. Or the creases in your hand warping and swirling after staring at them intensely. Auras of light surrounding people or objects. Surfaces may ripple or appear altered in color or texture. There are people who have persistent LSD-like effects, and it's a condition called HPPD. I don't think you have it.
Perhaps most importantly, LSD does NOT cause 'real' hallucinations either during or after ingestion. That is to say, unless you're on some enormous dose of LSD, you are typically somewhat aware of what is and is not real. The same applies to the 'flashbacks.' You do not need to worry that the car you saw was not real. I would NOT recommend doing LSD and crossing the street, but LSD does not cause that kind of hallucination - mainly just distortions in size/shape/color/perception.
In case you're wondering, real hallucinations are when you see something that isn't real, but you are convinced it is - and you may even interact with it/him/her. This is seen in schizophrenia, dementia, and other mental illnesses. Some pharmaceutical drugs, and plants will cause effects like this, but are extremely dangerous - when you take a deliriant, you experience strong hallucinations that cannot be distinguished from reality, and you can imagine how this could be dangerous.
DISCLAIMER: The above post focuses on LSD only because it is well known, but LSD is NOT 'the bad guy' amongst hallucinogens. LSD is not necessarily more likely to cause HPPD or 'flashbacks' than other drugs. Many people believe that it's much safer to do mushrooms, Hawaiin baby woodrose seeds, cough syrup, or other drugs. It isn't. In fact, LSD is actually quite benign in comparison to some of the new research chemicals floating around at clubs - many of which have a totally unknown safety profile, and have been found to be MUCH more likely to cause flashbacks. All I can say is do your research (wikipedia and erowid are good for this). And whatever you do, never huff gasoline or inhale anything! LSD is like candy compared to how bad inhalants are to your brain/body.
PS: Even if there is nothing really wrong with you, if this continues to be a problem, you may need to see your doctor or a psychiatrist. But I think most likely (with hope) you will go on living your life, get preoccupied with some new hobby, girlfriend or extracurricular activity, and totally forget that any of this happened.