I suppose a psychiatrist might be best person to ask, but I would guess so. I'm 9 months out from a loss myself, and I've noticed an increase in anxiety (although I have a pre-existing anxiety problem). I think if you bury the grief and try to deny it, it'll come out in other ways. I've ignored mine as well, and it's been manifesting itself (I think) in random feelings of sadness, anger, anxiety, along with chronic heartburn and teeth grinding.

These are all "triggers" or symptoms of PTSD.. If you have not done so, i would strongly suggest talking with a psychologist or LCSW , a therapist basically, to talk about some of this.
It took me almost 6 months to realize that I was having symptoms of PTSD, and anxiety attacks. At first I just thought they were bad Asthma attacks.

Triggers are things that you avoid, that remind you the event -- smells, sounds, people, places.. ect.
You may also have things such as difficutly sleeping, heightened sense of awareness 0r always being on gaurd, increased irritability, agitation, nightmares and flashbacks.

Grief is patient , if you don't make time for it, it will sneak in when your guard is down. Also there is a shock of sorts at first,(many cannot cry at first, because of this) later when your heart and brain are on the same page, then the grief needs to be attended to. Even if its hurts.
Prior to PTSD is the PTS part. Understanding the loss, accepting and grieving it now, will allow you to move on.
I am sorry for the loss that brings you here.

Losing your Dad even as a grown up is traumatic. Good and bad of them till causes grief. Reconciling things you wish you had said, or what you didn't say can cause guilt. Anxiety of the loss is helped by talking it out. With a therapist or here, with others that have also gone through it.

You might also write him a letter. To get out words unsaid. This often happens if when they were ill prior to passing. It's our nature only talk of light things, not the deep stuff, if they are in pain. The deep stuff can be put in the letter. So you address it. (and he sees it, if you are of that belief)

During a PA, a ice cold drink of water can help grounding, feeling the cold in your mouth bringing you back to the "now". Letting the PA run it's course and wane away.

I have tingles of anxiety every year around my brother's "death date". I almost think part of it is HIM, tugging at my heart, from the other side, saying "Don't forget me! Don't forget me!", so I don't. I always make time whenever possible to think upon him, meditate upon him, to try and commune with him emotionally, maybe try to connect with him and hang out with him in a dream.

You HAVE to make time for this, to sink into the well and meditate on this person and what they meant to you, maybe cry a little, or cry a lot. But, I agree, you have to rejoin the living, in THIS world, too. It's about balance, making time for both.

If you're trying to avoid hurting, it's a futile effort. It's OK to be upset. Only by going through pain will you gently begin to push forward. The pain hurts less when you allow yourself to sink into it. This avoidance of pain is causing fear which is causing panic. Embrace that which scares you. Embrace it with love. Then, with time and patience, it won't scare you anymore.

Well, "probably not any of my medication" isn't necessarily true since I have experienced side effects on medication in the 1% of the population. BUT....when you actively deny, when you refuse to grieve (let's face it, it's frightening to grieve), when you tell everyone you're "okay".....panic attacks can be the result. BLAMING yourself and feeling guilty is NOT okay. Many people put off trying to deal with the death of a loved one. Eventually, these people suffer. Some repress other important feelings, others express their suppressed grief in anger, all sorts of behaviors can emerge.

If you're taking a new medication and you had a panic attack, observe the next few weeks and talk to your therapist. If you don't have a therapist, find one, a certified grief counselor, preferably. And don't put any blame or judgment on yourself. Anxiety is part of the grieving process (not the mourning process, that's different and comes later). As far as PTSD is concerned (as mentioned by other posters), this is a REAL and bizarre event that can literally overtake you anywhere, any time. Intrusive thoughts, increased anxiety, not being able to turn "off" the "voice in your head" that goes over and over the event: all signs of PTSD. Counter conditioning takes months in a human being but it can be done. Ask your therapist.